IS-IS Lab 23 Several L1 Areas Attached to a Single Router
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Download Lab: VIRL | EVE-NG | GNS3
Image requirements:
Cisco IOSv (vios-adventerprisek9-m.vmdk.SPA.156-2.T)
Introduction:
Multiple L1 areas can be configured on the single router with the help of IS-IS tags. Every IS-IS L1 area must use an L1/L2 router to communicate with devices outside of its area. If there are multiple L1 areas in topology, concentrated in one physical location to form the border with the L2 area, there would be a lot of L1/L2 nodes to make it happen, this configuration introduces complexity and unnecessary consumption of resources. In this lab, you will configure a single router attached to multiple L1 areas and one L2 area to conserve resources and implement the neat design to ease future troubleshooting.
Nodes Access:
Enable: cisco
Username: cisco
Password: cisco
Topology:
Scenario:
Most of the routers in the topology have been configured to route IPv4 and IPV6 using IS-IS except "A" routers, this group of routers has one node A1 which is L1/L2 router and it will connect several L1 areas to the L2 area. Router A1 will run four different IS-IS processes, one to connect to the core over L2 adjacency, and three other processes will be configured for L1 areas. IS-IS processes for L1 areas named after its area ID.
Lab tasks:
1. Configure IS-IS on the router A1 with the default IS-IS process tag to connect to the core infrastructure. IS-type for this process will be L2-only as well as circuit-id for the interface connecting to the C1 router. The area-ID is A00A.
2. Verify that L2 IS-IS neighborship formed between A1 and the core router C1. Confirm that A1 able to ping IP addresses of the loopback0 interfaces of L1 routers B2, D2, and E2, this will ensure that router A1 is successfully communicated with the rest of the topology.
3. Configure the first L1 area A000, enable IS-IS process A000 on the router A1, router A2 will be configured using the default tag for the IS-IS process.
4. Verify the proper configuration of the A000 area. Check for neighborship formation between routers A1 and A2. Make sure that node A1 is able to ping A2's loopback0 interfaces' IP address.
5. Proceed to configure the second L1 area A001, router A1 configured with the IS-IS process tag of A001, while all configuration on the A3 will be performed with default parameters.
6. Repeat step 4 for the area A001.
7. Finally, configure area A002, router A1 has A002 as an IS-IS process tag. Router A4 configured with default parameters.
8. Again, confirm the proper configuration of area A002.
9. Test connectivity from L1 "A" routers to router E2.
10. Understand why connectivity test from L1 "A" routers failed.
11. Implement a solution.
12. Test a solution.
Lab procedure:
Step1: Acess CLI of router A1, enter IS-IS router mode, type the NET address of 49.A00A.0000.0000.00A1.00, change IS-Type to L2 only, then configure IS-IS on the interfaces G0/2 and Lo0 with circuit-type L2, enable IS-IS for both IPv4 and IPv6:
A1(config)#router isis
A1(config-router)#net 49.A00A.0000.0000.00A1.00
A1(config-router)#is-type level-2-only
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/2
A1(config-if)#isis circuit-type level-2-only
A1(config-if)#ip router isis
A1(config-if)#ipv6 router isis
A1(config-if)# end
!
A1(config)#interface lo0
A1(config-if)#isis circuit-type level-2-only
A1(config-if)#ip router isis
A1(config-if)#ipv6 router isis
Step2: Verify that A1 has L2 adjacency with router C1, ping other L1 routers in the topology:
A1#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 9 C1.02
A1#show isis protocol
IS-IS Router: <Null Tag>
System Id: 0000.0000.00A1.00 IS-Type: level-2
Manual area address(es):
49.a00a
Routing for area address(es):
49.a00a
Interfaces supported by IS-IS:
Loopback0 - IP - IPv6
GigabitEthernet0/2 - IP - IPv6
Redistribute:
static (on by default)
Distance for L2 CLNS routes: 110
RRR level: none
Generate narrow metrics: none
Accept narrow metrics: none
Generate wide metrics: level-1-2
Accept wide metrics: level-1-2
A1#ping 192.168.0.7
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.7, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 6/7/9 ms
A1#ping 192.168.0.9
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.9, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/5 ms
A1#ping 2001:DB8:b:0:1::d
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::D, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/5/11 ms
A1#
Step3: Configure router A1 for L1 area A000, first enter router IS-IS mode with process tag of A000 then assign the NET address of 49.A000.1000.0000.00A1.00, leave default IS-type, configure metric style wide. Enable interface G0/1 for IPv4 and IPv6 with a process tag of A000. Configure IS-IS on the router A3 with the default tag, assign NET of 49.A000.0000.0000.00A2.00, change IS-Type to L1, enable interfaces G0/1 and loopback0 for both IPv4 and IPv6 IS-IS:
A1(config)#router isis A000
A1(config-router)#net 49.A000.1000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/1
A1(config-if)#ip router isis A000
A1(config-if)#ipv6 router isis A000
A1(config-if)# end
!
!
A2(config)#router isis
A2(config-router)#net 49.A000.0000.0000.00A2.00
A2(config-router)#log-adjacency-changes
A2(config-router)#is-type level-1
A2(config-router)#metric-style wide
A2(config-router)#exit
!
A2(config)#interface range g0/1, lo0
A2(config-if-range)#ip router isis
A2(config-if-range)#ipv6 router isis
A2(config-if-range)#isis circuit-type level-1
Step4: Verify proper IS-IS configuration in the area A000:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 27 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
A2#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
A1 L1 Gi0/1 10.0.0.25 UP 29 A2.01
A2#
This output shows that A1 has two neighbors, one L2 neighbor for the null tag which is the C1 router. Another neighbor router A2 which appears under the A000 tag. This means that both of these neighbors are in separate IS-IS topologies. Displaying database on the router A1 will prove that each process tag has its own database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000009 0xEB2B 682/* 0/0/0
A1.01-00 * 0x00000002 0x2B9D 645/* 0/0/0
B1.00-00 0x00000007 0xA811 732/1198 0/0/0
B1.02-00 0x00000003 0x465F 739/1198 0/0/0
C1.00-00 0x00000008 0x74B8 685/1199 0/0/0
C2.00-00 0x00000008 0x9B50 869/1198 0/0/0
C2.01-00 0x00000003 0x4A3B 883/1198 0/0/0
C2.03-00 0x00000003 0xBEA4 800/1198 0/0/0
D1.00-00 0x00000007 0x2A43 765/1198 0/0/0
D1.02-00 0x00000003 0x5214 659/1198 0/0/0
E1.00-00 0x00000007 0x4C17 965/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000005 0x05F0 691/1199 0/0/0
A2.01-00 0x00000001 0x82CE 692/1199 0/0/0
A1.00-00 * 0x00000004 0xB25B 692/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0xCE87 698/* 0/0/0
A1#
Ping loopback0's IP addresses of A2:
A1#ping 192.168.0.9
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.9, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/6 ms
A1#ping 2001:Db8:b:0:1::b
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::B, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/5 ms
A1#
Successful ping indicates that area A000 has been configured properly.
Step5: Configuring area A001. Enter IS-IS router mode with process tag of A001, assign the NET address of 49.A001.2000.0000.00A1.00, change metric-style to wide, IS-type stays default, configure interface g0/3 for both IPv4 and IPv6 IS-IS using the tag of A001. Configure router A3 with default tag, assign the NET address of 49.A001.0000.0000.00A3.00, change IS-type to L1-only, metric-style is wide, both G0/1 and lo0 are participating for IPv4 and IPv6 IS-IS:
A1(config)#router isis A001
A1(config-router)#net 49.A001.2000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/3
A1(config-if)#ip router isis A001
A1(config-if)#ipv6 router isis A001
!
!
A3(config)#router isis
A3(config-router)#net 49.A001.0000.0000.00A3.00
A3(config-router)#is-type level-1
A3(config-router)#log-adjacency-changes
A3(config-router)#metric-style wide
A3(config-router)#exit
!
A3(config)#interface range g0/1, lo0
A3(config-if-range)#isis circuit-type level-1
A3(config-if-range)#ip router isis
A3(config-if-range)#ipv6 router isis
A3(config-if-range)# exit
Step6: Verify IS-IS configuration for area A001:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 25 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 29 A1.01
A1#
Now router A1 has one more neighbor router A3, under the tag A001.
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000D 0xE32F 564/* 0/0/0
A1.01-00 * 0x00000004 0x279F 917/* 0/0/0
B1.00-00 0x00000009 0xA413 860/1198 0/0/0
B1.02-00 0x00000005 0x4261 889/1198 0/0/0
C1.00-00 0x0000000A 0x70BA 955/1199 0/0/0
C2.00-00 0x0000000A 0x9752 881/1198 0/0/0
C2.01-00 0x00000005 0x463D 1183/1198 0/0/0
C2.03-00 0x00000005 0xBAA6 898/1198 0/0/0
D1.00-00 0x00000009 0x2645 847/1198 0/0/0
D1.02-00 0x00000005 0x4E16 856/1198 0/0/0
E1.00-00 0x00000009 0x4819 942/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000007 0x01F2 924/1199 0/0/0
A2.01-00 0x00000003 0x7ED0 630/1199 0/0/0
A1.00-00 * 0x00000006 0xAE5D 793/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000006 0xCA89 880/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000005 0x386F 940/1196 0/0/0
A1.00-00 * 0x00000004 0xF2AA 939/* 0/0/0
A1.01-00 * 0x00000001 0x9985 940/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0x9965 945/* 0/0/0
A new database for IS-IS process A001 appears at the bottom of the output.
A1#ping 192.168.0.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.11, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
A1#ping 2001:DB8:b:0:1::4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/5 ms
A1#
Ping to A3's loopback0 IP addresses confirms that area A001 has been configured successfully.
Step7: Configuring area A002. Router A1 configured with the tag of A002, has the NET address of 49.A002.3000.0000.00A1.00, metric-style is wide, IS-type remains the default, interface G0/4 enabled for both IPv4 and IPv6 IS-IS with tag A002. Router A4 configured with the default tag. Has the NET address of 49.A002.0000.0000.00A4.00, IS-type changed to L1-only, metric-style is wide, interfaces G0/1 and Lo0 are both participating in the IPv4 and IPv6 IS-IS with circuit-type L1:
A1(config)#router isis A002
A1(config-router)#net 49.A002.3000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/4
A1(config-if)#ip router isis A002
A1(config-if)#ipv6 router isis A002
A1(config-if)#exit
!
!
A4(config)#router isis
A4(config-router)#net 49.A002.0000.0000.00A4.00
A4(config-router)#is-type level-1
A4(config-router)#metric-style wide
A4(config-router)#log-adjacency-changes
A4(config-router)#exit
!
A4(config)#interface range g0/1, lo0
A4(config-if-range)#isis circuit-type level-1
A4(config-if-range)#ip router isis
A4(config-if-range)#ipv6 router isis
A4(config-if-range)# exit
Step8: Lastly verify the area A002:
A1#show isis neighbors Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 29 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 29 A1.01
Tag A002:
System Id Type Interface IP Address State Holdtime Circuit Id
A4 L1 Gi0/4 10.0.0.46 UP 8 A4.01
A1#
Now the output shows the complete outcome, router A1 as intended has four neighbors one with L2 adjacency and three with L1 adjacencies. Three L1 areas have been attached to a single router. Router A1 has four separate IS-IS topologies as shown in the output below:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000010 0xDD32 665/* 0/0/0
A1.01-00 * 0x00000006 0x23A1 541/* 0/0/0
B1.00-00 0x0000000C 0x9E16 1008/1198 0/0/0
B1.02-00 0x00000008 0x3C64 1145/1198 0/0/0
C1.00-00 0x0000000C 0x6CBC 505/1199 0/0/0
C2.00-00 0x0000000D 0x9155 1145/1198 0/0/0
C2.01-00 0x00000007 0x423F 692/1198 0/0/0
C2.03-00 0x00000008 0xB4A9 1064/1198 0/0/0
D1.00-00 0x0000000C 0x2048 1033/1198 0/0/0
D1.02-00 0x00000008 0x4819 1084/1198 0/0/0
E1.00-00 0x0000000B 0x441B 587/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000009 0xFCF4 480/1199 0/0/0
A2.01-00 0x00000006 0x78D3 964/1199 0/0/0
A1.00-00 * 0x00000009 0xA860 999/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000009 0xC48C 1197/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000008 0x3272 1160/1199 0/0/0
A1.00-00 * 0x00000006 0xEEAC 535/* 0/0/0
A1.01-00 * 0x00000003 0x9587 421/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000006 0x9567 470/* 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x00000007 0xCAE8 771/1199 0/0/0
A4.01-00 0x00000002 0x64C7 768/1199 0/0/0
A1.00-00 * 0x00000006 0xDFB7 773/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0xC11A 726/* 0/0/0
A1#
Confirm connectivity to router A4:
A1#ping 192.168.0.12
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.12, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
A1#ping 2001:DB8:b:0:1::5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/8 ms
A1#
The result of ping is positive, proves that area A002 has been enabled in the right way.
Step9: Test if routers A2, A3, and A4 able to ping IP address in another L1 area:
A2#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A2#
A3#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A3#
A4#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A4#
All three routers failed to ping E2's IP address, the next step hypothesizes what is happening with connectivity.
Step10: To understand the issue occurring in the previous step, further investigation is required, starting from router A2 identify if node learns any IS-IS prefixes:
A2#show ip router isis
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is not set
A2#show ipv6 route isis
IPv6 Routing Table - default - 4 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
RL - RPL, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
la - LISP alt, lr - LISP site-registrations, ld - LISP dyn-eid
lA - LISP away, a - Application
A2#
From the empty routing table for IS-IS protocol, the conclusion can be drawn that L1/L2 router A1 does not send any routes to this node, a question rises why not?
Let's interrogate local IS-IS database:
A2#show isis database
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 * 0x00000011 0xECFC 968/* 0/0/0
A2.01-00 * 0x0000000D 0x6ADA 983/* 0/0/0
A1.00-00 0x00000010 0x9A67 906/1199 0/0/0
A2#
Ok! This output of the database shows quite interesting information, the LSP of router A1 does not have ATT bit set to 1 instead it is set to 0. Recall that by default every L1 IS-IS area is like OSPF's totally stub area and the nearest L1/L2 router suppose to send its LSP with an attached bit set to 1 then the L1 router will install default route into its routing table but in this case, it does not!
Why A1 which is configured to be L1/L2 node does not advertise its LSP with ATT bit set to 1? Switching thoughts to router A1! Examine A1 database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000018 0xCD3A 925/* 0/0/0
A1.01-00 * 0x0000000E 0x13A9 568/* 0/0/0
B1.00-00 0x00000013 0x901D 382/1198 0/0/0
B1.02-00 0x0000000F 0x2E6B 393/1198 0/0/0
C1.00-00 0x00000014 0x5CC4 594/1199 0/0/0
C2.00-00 0x00000015 0x815D 894/1198 0/0/0
C2.01-00 0x0000000F 0x3247 745/1198 0/0/0
C2.03-00 0x00000010 0xA4B1 1186/1198 0/0/0
D1.00-00 0x00000014 0x1050 1152/1198 0/0/0
D1.02-00 0x00000010 0x3821 928/1198 0/0/0
E1.00-00 0x00000014 0x3224 968/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000012 0xEAFD 908/1199 0/0/0
A2.01-00 0x0000000E 0x68DB 953/1199 0/0/0
A1.00-00 * 0x00000011 0x9868 920/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000011 0xB494 1140/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000010 0x227A 1073/1199 0/0/0
A1.00-00 * 0x0000000E 0xDEB4 783/* 0/0/0
A1.01-00 * 0x0000000B 0x858F 697/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000E 0x856F 549/* 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x0000000F 0xBAF0 886/1199 0/0/0
A4.01-00 0x0000000A 0x54CF 530/1199 0/0/0
A1.00-00 * 0x0000000E 0xCFBF 780/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000C 0xB122 685/* 0/0/0
A1#
This output shows that the database contains four distinct IS-IS topologies identified by IS-IS process tags:
Tag "null" has the database for L2 area A00A which brings connection to the rest of topology only for router A1, meaning that router A1 and its subnets accessible to the rest of routers in the topology who connected by any means to L2 backbone.
Tag "A000" and the rest of IS-IS process tags have the same fate, all of them show that databases for these tags do not have any other LSPs but only A1's LSP. Practically speaking that L1/L2 node for each "tag" is configured to be in both L1 and L2 areas but has no connection to the L2 core router C1 that is why A1 does not technically act as L1/L2 node!
To fix this problem, think of the A1 router as a physical device that has been connected to three L1 areas, these areas are independent of each other therefore they need three distinct L1/L2 nodes to communicate with the rest of the topology. Router A1 is the only device those areas have been connected to and logical means of communication with L2 backbone has to be provided to each L1 areas separated by tags on the router A1.
Solution: Three more physical links could be added between router C1 and A1 then configure each of interfaces with its own IS-IS tag correlated to each L1 area. But for this lab, only one link is present between those routers, to overcome the problem of a limited amount of physical interfaces, sub-interfaces will be used. Interface G0/2 on both sides will be partitioned to have sub-interfaces G0/2.10 for the tag A000, g0/2.11 for the tag A001, and g0/2.12 for the tag A002.
Step11: Implement solution:
Configure router C1:
C1(config)#interface g0/2.10
C1(config-subif)#encapsulation dot1Q 10
C1(config-subif)#ip address 10.0.1.1 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
!C1(config)#interface g0/2.11
C1(config-subif)#encapsulation dot1Q 11
C1(config-subif)#ip address 10.0.1.5 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
!
C1(config)#interface g0/2.12
C1(config-subif)#encapsulation dot1Q 12
C1(config-subif)#ip address 10.0.1.9 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
Configure router A1:
A1(config)#interface g0/2.10
A1(config-subif)#encapsulation dot1Q 10
A1(config-subif)#ip address 10.0.1.2 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A000
A1(config-subif)#ip router isis A000
!A1(config)#interface g0/2.11
A1(config-subif)#encapsulation dot1Q 11
A1(config-subif)#ip address 10.0.1.6 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A001
A1(config-subif)#ip router isis A001
!
A1(config)#interface g0/2.12
A1(config-subif)#encapsulation dot1Q 12
A1(config-subif)#ip address 10.0.1.10 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A002
A1(config-subif)#ip router isis A002
Step12: Test the solution. Begin with verifying IS-IS neighborships on the router A1:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 28 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
C1 L2 Gi0/2.10 10.0.1.1 UP 21 A1.02
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 27 A1.01
C1 L2 Gi0/2.11 10.0.1.5 UP 21 A1.02
Tag A002:
System Id Type Interface IP Address State Holdtime Circuit Id
A4 L1 Gi0/4 10.0.0.46 UP 9 A4.01
C1 L2 Gi0/2.12 10.0.1.9 UP 24 A1.02
A1#
Router A1 is now having neighborship with router C1 for every L1 tag. Let's see what is going on with the database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000023 0xB745 940/* 0/0/0
A1.01-00 * 0x00000018 0xFEB3 1091/* 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x0000001A 0xDA06 772/1199 0/0/0
A2.01-00 0x00000017 0x56E4 975/1199 0/0/0
A1.00-00 * 0x0000001B 0xE19A 1011/* 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 * 0x0000001B 0x45A8 1087/* 0/0/0
A1.02-00 * 0x00000004 0x8F16 872/* 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000018 0x1282 779/1199 0/0/0
A1.00-00 * 0x00000018 0xA252 467/* 1/0/0
A1.01-00 * 0x00000014 0x7398 870/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 * 0x00000018 0x84EA 463/* 0/0/0
A1.02-00 * 0x00000004 0xFE86 1099/* 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x00000018 0xA8F9 1058/1199 0/0/0
A4.01-00 0x00000013 0x42D8 765/1199 0/0/0
A1.00-00 * 0x00000019 0xE209 1151/* 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 * 0x00000016 0x4FEA 514/* 0/0/0
A1.02-00 * 0x00000003 0x70F5 611/* 0/0/0
A1#
The output has changed since the last time, for every L1 tag, there are L2 LSPs from other L2 and L1/L2 routers. Also for the Level 1 IS-IS database, A1's LSP has ATT bit set to 1.
Next, check router A2, starting with database:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 * 0x0000001C 0xD608 1158/* 0/0/0
A2.01-00 * 0x00000018 0x54E5 617/* 0/0/0
A1.00-00 0x0000001D 0xDD9C 1171/1199 1/0/0
A2#
Finally, the LSP from router A1 has an ATT bit set. Next, verify the routing table:
A2#show ip route isis
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is 10.0.0.25 to network 0.0.0.0
i*L1 0.0.0.0/0 [115/10] via 10.0.0.25, 01:16:57, GigabitEthernet0/1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
i L1 10.0.1.0/30 [115/20] via 10.0.0.25, 01:17:13, GigabitEthernet0/1
A2#
A2#show ipv6 route isis
IPv6 Routing Table - default - 5 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
RL - RPL, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
la - LISP alt, lr - LISP site-registrations, ld - LISP dyn-eid
lA - LISP away, a - Application
I1 ::/0 [115/10]
via FE80::F816:3EFF:FE0E:70D3, GigabitEthernet0/1
A2#
For both IPv4 and IPv6, there is default route, router A2 should be able to ping some destinations in other L1 areas:
A2#ping 192.168.0.8
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/6/8 ms
A2#ping 2001:DB8:b:0:1::d
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::D, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/11/37 ms
A2#
The same goes for router A3 and A4, they also should be able to ping remote IP addresses of other L1 areas in the topology.
Download Lab: VIRL | EVE-NG | GNS3
Image requirements:
Cisco IOSv (vios-adventerprisek9-m.vmdk.SPA.156-2.T)
Introduction:
Multiple L1 areas can be configured on the single router with the help of IS-IS tags. Every IS-IS L1 area must use an L1/L2 router to communicate with devices outside of its area. If there are multiple L1 areas in topology, concentrated in one physical location to form the border with the L2 area, there would be a lot of L1/L2 nodes to make it happen, this configuration introduces complexity and unnecessary consumption of resources. In this lab, you will configure a single router attached to multiple L1 areas and one L2 area to conserve resources and implement the neat design to ease future troubleshooting.
Nodes Access:
Enable: cisco
Username: cisco
Password: cisco
Topology:
Scenario:
Most of the routers in the topology have been configured to route IPv4 and IPV6 using IS-IS except "A" routers, this group of routers has one node A1 which is L1/L2 router and it will connect several L1 areas to the L2 area. Router A1 will run four different IS-IS processes, one to connect to the core over L2 adjacency, and three other processes will be configured for L1 areas. IS-IS processes for L1 areas named after its area ID.
Lab tasks:
1. Configure IS-IS on the router A1 with the default IS-IS process tag to connect to the core infrastructure. IS-type for this process will be L2-only as well as circuit-id for the interface connecting to the C1 router. The area-ID is A00A.
2. Verify that L2 IS-IS neighborship formed between A1 and the core router C1. Confirm that A1 able to ping IP addresses of the loopback0 interfaces of L1 routers B2, D2, and E2, this will ensure that router A1 is successfully communicated with the rest of the topology.
3. Configure the first L1 area A000, enable IS-IS process A000 on the router A1, router A2 will be configured using the default tag for the IS-IS process.
4. Verify the proper configuration of the A000 area. Check for neighborship formation between routers A1 and A2. Make sure that node A1 is able to ping A2's loopback0 interfaces' IP address.
5. Proceed to configure the second L1 area A001, router A1 configured with the IS-IS process tag of A001, while all configuration on the A3 will be performed with default parameters.
6. Repeat step 4 for the area A001.
7. Finally, configure area A002, router A1 has A002 as an IS-IS process tag. Router A4 configured with default parameters.
8. Again, confirm the proper configuration of area A002.
9. Test connectivity from L1 "A" routers to router E2.
10. Understand why connectivity test from L1 "A" routers failed.
11. Implement a solution.
12. Test a solution.
Lab procedure:
Step1: Acess CLI of router A1, enter IS-IS router mode, type the NET address of 49.A00A.0000.0000.00A1.00, change IS-Type to L2 only, then configure IS-IS on the interfaces G0/2 and Lo0 with circuit-type L2, enable IS-IS for both IPv4 and IPv6:
A1(config)#router isis
A1(config-router)#net 49.A00A.0000.0000.00A1.00
A1(config-router)#is-type level-2-only
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/2
A1(config-if)#isis circuit-type level-2-only
A1(config-if)#ip router isis
A1(config-if)#ipv6 router isis
A1(config-if)# end
!
A1(config)#interface lo0
A1(config-if)#isis circuit-type level-2-only
A1(config-if)#ip router isis
A1(config-if)#ipv6 router isis
Step2: Verify that A1 has L2 adjacency with router C1, ping other L1 routers in the topology:
A1#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 9 C1.02
A1#show isis protocol
IS-IS Router: <Null Tag>
System Id: 0000.0000.00A1.00 IS-Type: level-2
Manual area address(es):
49.a00a
Routing for area address(es):
49.a00a
Interfaces supported by IS-IS:
Loopback0 - IP - IPv6
GigabitEthernet0/2 - IP - IPv6
Redistribute:
static (on by default)
Distance for L2 CLNS routes: 110
RRR level: none
Generate narrow metrics: none
Accept narrow metrics: none
Generate wide metrics: level-1-2
Accept wide metrics: level-1-2
A1#ping 192.168.0.7
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.7, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 6/7/9 ms
A1#ping 192.168.0.9
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.9, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/5 ms
A1#ping 2001:DB8:b:0:1::d
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::D, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/5/11 ms
A1#
Step3: Configure router A1 for L1 area A000, first enter router IS-IS mode with process tag of A000 then assign the NET address of 49.A000.1000.0000.00A1.00, leave default IS-type, configure metric style wide. Enable interface G0/1 for IPv4 and IPv6 with a process tag of A000. Configure IS-IS on the router A3 with the default tag, assign NET of 49.A000.0000.0000.00A2.00, change IS-Type to L1, enable interfaces G0/1 and loopback0 for both IPv4 and IPv6 IS-IS:
A1(config)#router isis A000
A1(config-router)#net 49.A000.1000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/1
A1(config-if)#ip router isis A000
A1(config-if)#ipv6 router isis A000
A1(config-if)# end
!
!
A2(config)#router isis
A2(config-router)#net 49.A000.0000.0000.00A2.00
A2(config-router)#log-adjacency-changes
A2(config-router)#is-type level-1
A2(config-router)#metric-style wide
A2(config-router)#exit
!
A2(config)#interface range g0/1, lo0
A2(config-if-range)#ip router isis
A2(config-if-range)#ipv6 router isis
A2(config-if-range)#isis circuit-type level-1
Step4: Verify proper IS-IS configuration in the area A000:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 27 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
A2#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
A1 L1 Gi0/1 10.0.0.25 UP 29 A2.01
A2#
This output shows that A1 has two neighbors, one L2 neighbor for the null tag which is the C1 router. Another neighbor router A2 which appears under the A000 tag. This means that both of these neighbors are in separate IS-IS topologies. Displaying database on the router A1 will prove that each process tag has its own database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000009 0xEB2B 682/* 0/0/0
A1.01-00 * 0x00000002 0x2B9D 645/* 0/0/0
B1.00-00 0x00000007 0xA811 732/1198 0/0/0
B1.02-00 0x00000003 0x465F 739/1198 0/0/0
C1.00-00 0x00000008 0x74B8 685/1199 0/0/0
C2.00-00 0x00000008 0x9B50 869/1198 0/0/0
C2.01-00 0x00000003 0x4A3B 883/1198 0/0/0
C2.03-00 0x00000003 0xBEA4 800/1198 0/0/0
D1.00-00 0x00000007 0x2A43 765/1198 0/0/0
D1.02-00 0x00000003 0x5214 659/1198 0/0/0
E1.00-00 0x00000007 0x4C17 965/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000005 0x05F0 691/1199 0/0/0
A2.01-00 0x00000001 0x82CE 692/1199 0/0/0
A1.00-00 * 0x00000004 0xB25B 692/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0xCE87 698/* 0/0/0
A1#
Ping loopback0's IP addresses of A2:
A1#ping 192.168.0.9
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.9, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/6 ms
A1#ping 2001:Db8:b:0:1::b
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::B, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/5 ms
A1#
Successful ping indicates that area A000 has been configured properly.
Step5: Configuring area A001. Enter IS-IS router mode with process tag of A001, assign the NET address of 49.A001.2000.0000.00A1.00, change metric-style to wide, IS-type stays default, configure interface g0/3 for both IPv4 and IPv6 IS-IS using the tag of A001. Configure router A3 with default tag, assign the NET address of 49.A001.0000.0000.00A3.00, change IS-type to L1-only, metric-style is wide, both G0/1 and lo0 are participating for IPv4 and IPv6 IS-IS:
A1(config)#router isis A001
A1(config-router)#net 49.A001.2000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/3
A1(config-if)#ip router isis A001
A1(config-if)#ipv6 router isis A001
!
!
A3(config)#router isis
A3(config-router)#net 49.A001.0000.0000.00A3.00
A3(config-router)#is-type level-1
A3(config-router)#log-adjacency-changes
A3(config-router)#metric-style wide
A3(config-router)#exit
!
A3(config)#interface range g0/1, lo0
A3(config-if-range)#isis circuit-type level-1
A3(config-if-range)#ip router isis
A3(config-if-range)#ipv6 router isis
A3(config-if-range)# exit
Step6: Verify IS-IS configuration for area A001:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 25 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 29 A1.01
A1#
Now router A1 has one more neighbor router A3, under the tag A001.
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000D 0xE32F 564/* 0/0/0
A1.01-00 * 0x00000004 0x279F 917/* 0/0/0
B1.00-00 0x00000009 0xA413 860/1198 0/0/0
B1.02-00 0x00000005 0x4261 889/1198 0/0/0
C1.00-00 0x0000000A 0x70BA 955/1199 0/0/0
C2.00-00 0x0000000A 0x9752 881/1198 0/0/0
C2.01-00 0x00000005 0x463D 1183/1198 0/0/0
C2.03-00 0x00000005 0xBAA6 898/1198 0/0/0
D1.00-00 0x00000009 0x2645 847/1198 0/0/0
D1.02-00 0x00000005 0x4E16 856/1198 0/0/0
E1.00-00 0x00000009 0x4819 942/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000007 0x01F2 924/1199 0/0/0
A2.01-00 0x00000003 0x7ED0 630/1199 0/0/0
A1.00-00 * 0x00000006 0xAE5D 793/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000006 0xCA89 880/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000005 0x386F 940/1196 0/0/0
A1.00-00 * 0x00000004 0xF2AA 939/* 0/0/0
A1.01-00 * 0x00000001 0x9985 940/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0x9965 945/* 0/0/0
A new database for IS-IS process A001 appears at the bottom of the output.
A1#ping 192.168.0.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.11, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
A1#ping 2001:DB8:b:0:1::4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/5 ms
A1#
Ping to A3's loopback0 IP addresses confirms that area A001 has been configured successfully.
Step7: Configuring area A002. Router A1 configured with the tag of A002, has the NET address of 49.A002.3000.0000.00A1.00, metric-style is wide, IS-type remains the default, interface G0/4 enabled for both IPv4 and IPv6 IS-IS with tag A002. Router A4 configured with the default tag. Has the NET address of 49.A002.0000.0000.00A4.00, IS-type changed to L1-only, metric-style is wide, interfaces G0/1 and Lo0 are both participating in the IPv4 and IPv6 IS-IS with circuit-type L1:
A1(config)#router isis A002
A1(config-router)#net 49.A002.3000.0000.00A1.00
A1(config-router)#metric-style wide
A1(config-router)#log-adjacency-changes
A1(config-router)#exit
!
A1(config)#interface g0/4
A1(config-if)#ip router isis A002
A1(config-if)#ipv6 router isis A002
A1(config-if)#exit
!
!
A4(config)#router isis
A4(config-router)#net 49.A002.0000.0000.00A4.00
A4(config-router)#is-type level-1
A4(config-router)#metric-style wide
A4(config-router)#log-adjacency-changes
A4(config-router)#exit
!
A4(config)#interface range g0/1, lo0
A4(config-if-range)#isis circuit-type level-1
A4(config-if-range)#ip router isis
A4(config-if-range)#ipv6 router isis
A4(config-if-range)# exit
Step8: Lastly verify the area A002:
A1#show isis neighbors Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 29 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 29 A1.01
Tag A002:
System Id Type Interface IP Address State Holdtime Circuit Id
A4 L1 Gi0/4 10.0.0.46 UP 8 A4.01
A1#
Now the output shows the complete outcome, router A1 as intended has four neighbors one with L2 adjacency and three with L1 adjacencies. Three L1 areas have been attached to a single router. Router A1 has four separate IS-IS topologies as shown in the output below:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000010 0xDD32 665/* 0/0/0
A1.01-00 * 0x00000006 0x23A1 541/* 0/0/0
B1.00-00 0x0000000C 0x9E16 1008/1198 0/0/0
B1.02-00 0x00000008 0x3C64 1145/1198 0/0/0
C1.00-00 0x0000000C 0x6CBC 505/1199 0/0/0
C2.00-00 0x0000000D 0x9155 1145/1198 0/0/0
C2.01-00 0x00000007 0x423F 692/1198 0/0/0
C2.03-00 0x00000008 0xB4A9 1064/1198 0/0/0
D1.00-00 0x0000000C 0x2048 1033/1198 0/0/0
D1.02-00 0x00000008 0x4819 1084/1198 0/0/0
E1.00-00 0x0000000B 0x441B 587/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000009 0xFCF4 480/1199 0/0/0
A2.01-00 0x00000006 0x78D3 964/1199 0/0/0
A1.00-00 * 0x00000009 0xA860 999/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000009 0xC48C 1197/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000008 0x3272 1160/1199 0/0/0
A1.00-00 * 0x00000006 0xEEAC 535/* 0/0/0
A1.01-00 * 0x00000003 0x9587 421/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000006 0x9567 470/* 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x00000007 0xCAE8 771/1199 0/0/0
A4.01-00 0x00000002 0x64C7 768/1199 0/0/0
A1.00-00 * 0x00000006 0xDFB7 773/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000004 0xC11A 726/* 0/0/0
A1#
Confirm connectivity to router A4:
A1#ping 192.168.0.12
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.12, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
A1#ping 2001:DB8:b:0:1::5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/8 ms
A1#
The result of ping is positive, proves that area A002 has been enabled in the right way.
Step9: Test if routers A2, A3, and A4 able to ping IP address in another L1 area:
A2#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A2#
A3#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A3#
A4#ping 192.168.0.8Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
A4#
All three routers failed to ping E2's IP address, the next step hypothesizes what is happening with connectivity.
Step10: To understand the issue occurring in the previous step, further investigation is required, starting from router A2 identify if node learns any IS-IS prefixes:
A2#show ip router isis
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is not set
A2#show ipv6 route isis
IPv6 Routing Table - default - 4 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
RL - RPL, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
la - LISP alt, lr - LISP site-registrations, ld - LISP dyn-eid
lA - LISP away, a - Application
A2#
From the empty routing table for IS-IS protocol, the conclusion can be drawn that L1/L2 router A1 does not send any routes to this node, a question rises why not?
Let's interrogate local IS-IS database:
A2#show isis database
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 * 0x00000011 0xECFC 968/* 0/0/0
A2.01-00 * 0x0000000D 0x6ADA 983/* 0/0/0
A1.00-00 0x00000010 0x9A67 906/1199 0/0/0
A2#
Ok! This output of the database shows quite interesting information, the LSP of router A1 does not have ATT bit set to 1 instead it is set to 0. Recall that by default every L1 IS-IS area is like OSPF's totally stub area and the nearest L1/L2 router suppose to send its LSP with an attached bit set to 1 then the L1 router will install default route into its routing table but in this case, it does not!
Why A1 which is configured to be L1/L2 node does not advertise its LSP with ATT bit set to 1? Switching thoughts to router A1! Examine A1 database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000018 0xCD3A 925/* 0/0/0
A1.01-00 * 0x0000000E 0x13A9 568/* 0/0/0
B1.00-00 0x00000013 0x901D 382/1198 0/0/0
B1.02-00 0x0000000F 0x2E6B 393/1198 0/0/0
C1.00-00 0x00000014 0x5CC4 594/1199 0/0/0
C2.00-00 0x00000015 0x815D 894/1198 0/0/0
C2.01-00 0x0000000F 0x3247 745/1198 0/0/0
C2.03-00 0x00000010 0xA4B1 1186/1198 0/0/0
D1.00-00 0x00000014 0x1050 1152/1198 0/0/0
D1.02-00 0x00000010 0x3821 928/1198 0/0/0
E1.00-00 0x00000014 0x3224 968/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x00000012 0xEAFD 908/1199 0/0/0
A2.01-00 0x0000000E 0x68DB 953/1199 0/0/0
A1.00-00 * 0x00000011 0x9868 920/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000011 0xB494 1140/* 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000010 0x227A 1073/1199 0/0/0
A1.00-00 * 0x0000000E 0xDEB4 783/* 0/0/0
A1.01-00 * 0x0000000B 0x858F 697/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000E 0x856F 549/* 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x0000000F 0xBAF0 886/1199 0/0/0
A4.01-00 0x0000000A 0x54CF 530/1199 0/0/0
A1.00-00 * 0x0000000E 0xCFBF 780/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x0000000C 0xB122 685/* 0/0/0
A1#
This output shows that the database contains four distinct IS-IS topologies identified by IS-IS process tags:
Tag "null" has the database for L2 area A00A which brings connection to the rest of topology only for router A1, meaning that router A1 and its subnets accessible to the rest of routers in the topology who connected by any means to L2 backbone.
Tag "A000" and the rest of IS-IS process tags have the same fate, all of them show that databases for these tags do not have any other LSPs but only A1's LSP. Practically speaking that L1/L2 node for each "tag" is configured to be in both L1 and L2 areas but has no connection to the L2 core router C1 that is why A1 does not technically act as L1/L2 node!
To fix this problem, think of the A1 router as a physical device that has been connected to three L1 areas, these areas are independent of each other therefore they need three distinct L1/L2 nodes to communicate with the rest of the topology. Router A1 is the only device those areas have been connected to and logical means of communication with L2 backbone has to be provided to each L1 areas separated by tags on the router A1.
Solution: Three more physical links could be added between router C1 and A1 then configure each of interfaces with its own IS-IS tag correlated to each L1 area. But for this lab, only one link is present between those routers, to overcome the problem of a limited amount of physical interfaces, sub-interfaces will be used. Interface G0/2 on both sides will be partitioned to have sub-interfaces G0/2.10 for the tag A000, g0/2.11 for the tag A001, and g0/2.12 for the tag A002.
Step11: Implement solution:
Configure router C1:
C1(config)#interface g0/2.10
C1(config-subif)#encapsulation dot1Q 10
C1(config-subif)#ip address 10.0.1.1 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
!C1(config)#interface g0/2.11
C1(config-subif)#encapsulation dot1Q 11
C1(config-subif)#ip address 10.0.1.5 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
!
C1(config)#interface g0/2.12
C1(config-subif)#encapsulation dot1Q 12
C1(config-subif)#ip address 10.0.1.9 255.255.255.252
C1(config-subif)#ipv6 enable
C1(config-subif)#ipv6 router isis
C1(config-subif)#ip router isis
Configure router A1:
A1(config)#interface g0/2.10
A1(config-subif)#encapsulation dot1Q 10
A1(config-subif)#ip address 10.0.1.2 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A000
A1(config-subif)#ip router isis A000
!A1(config)#interface g0/2.11
A1(config-subif)#encapsulation dot1Q 11
A1(config-subif)#ip address 10.0.1.6 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A001
A1(config-subif)#ip router isis A001
!
A1(config)#interface g0/2.12
A1(config-subif)#encapsulation dot1Q 12
A1(config-subif)#ip address 10.0.1.10 255.255.255.252
A1(config-subif)#ipv6 enable
A1(config-subif)#ipv6 router isis A002
A1(config-subif)#ip router isis A002
Step12: Test the solution. Begin with verifying IS-IS neighborships on the router A1:
A1#show isis neighbors
Tag null:
System Id Type Interface IP Address State Holdtime Circuit Id
C1 L2 Gi0/2 10.0.0.6 UP 28 A1.01
Tag A000:
System Id Type Interface IP Address State Holdtime Circuit Id
A2 L1 Gi0/1 10.0.0.26 UP 9 A2.01
C1 L2 Gi0/2.10 10.0.1.1 UP 21 A1.02
Tag A001:
System Id Type Interface IP Address State Holdtime Circuit Id
A3 L1 Gi0/3 10.0.0.42 UP 27 A1.01
C1 L2 Gi0/2.11 10.0.1.5 UP 21 A1.02
Tag A002:
System Id Type Interface IP Address State Holdtime Circuit Id
A4 L1 Gi0/4 10.0.0.46 UP 9 A4.01
C1 L2 Gi0/2.12 10.0.1.9 UP 24 A1.02
A1#
Router A1 is now having neighborship with router C1 for every L1 tag. Let's see what is going on with the database:
A1#show isis database
Tag null:
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 * 0x00000023 0xB745 940/* 0/0/0
A1.01-00 * 0x00000018 0xFEB3 1091/* 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A000:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 0x0000001A 0xDA06 772/1199 0/0/0
A2.01-00 0x00000017 0x56E4 975/1199 0/0/0
A1.00-00 * 0x0000001B 0xE19A 1011/* 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 * 0x0000001B 0x45A8 1087/* 0/0/0
A1.02-00 * 0x00000004 0x8F16 872/* 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A001:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A3.00-00 0x00000018 0x1282 779/1199 0/0/0
A1.00-00 * 0x00000018 0xA252 467/* 1/0/0
A1.01-00 * 0x00000014 0x7398 870/* 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 * 0x00000018 0x84EA 463/* 0/0/0
A1.02-00 * 0x00000004 0xFE86 1099/* 0/0/0
A1.00-00 0x00000016 0x4FEA 513/1198 0/0/0
A1.02-00 0x00000003 0x70F5 610/1198 0/0/0
Tag A002:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A4.00-00 0x00000018 0xA8F9 1058/1199 0/0/0
A4.01-00 0x00000013 0x42D8 765/1199 0/0/0
A1.00-00 * 0x00000019 0xE209 1151/* 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A1.00-00 0x00000023 0xB745 939/1198 0/0/0
A1.01-00 0x00000018 0xFEB3 1090/1198 0/0/0
B1.00-00 0x0000001C 0x7E26 567/1198 0/0/0
B1.02-00 0x00000018 0x1C74 686/1198 0/0/0
C1.00-00 0x00000025 0x825D 407/1199 0/0/0
C2.00-00 0x0000001D 0x7165 450/1198 0/0/0
C2.01-00 0x00000018 0x2050 514/1198 0/0/0
C2.03-00 0x00000018 0x94B9 1033/1198 0/0/0
D1.00-00 0x0000001C 0xFF58 468/1198 0/0/0
D1.02-00 0x00000019 0x262A 691/1198 0/0/0
E1.00-00 0x0000001D 0x202D 873/1198 0/0/0
A1.00-00 0x0000001B 0x45A8 1086/1198 0/0/0
A1.02-00 0x00000004 0x8F16 871/1198 0/0/0
A1.00-00 0x00000018 0x84EA 462/1198 0/0/0
A1.02-00 0x00000004 0xFE86 1098/1198 0/0/0
A1.00-00 * 0x00000016 0x4FEA 514/* 0/0/0
A1.02-00 * 0x00000003 0x70F5 611/* 0/0/0
A1#
The output has changed since the last time, for every L1 tag, there are L2 LSPs from other L2 and L1/L2 routers. Also for the Level 1 IS-IS database, A1's LSP has ATT bit set to 1.
Next, check router A2, starting with database:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL
A2.00-00 * 0x0000001C 0xD608 1158/* 0/0/0
A2.01-00 * 0x00000018 0x54E5 617/* 0/0/0
A1.00-00 0x0000001D 0xDD9C 1171/1199 1/0/0
A2#
Finally, the LSP from router A1 has an ATT bit set. Next, verify the routing table:
A2#show ip route isis
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is 10.0.0.25 to network 0.0.0.0
i*L1 0.0.0.0/0 [115/10] via 10.0.0.25, 01:16:57, GigabitEthernet0/1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
i L1 10.0.1.0/30 [115/20] via 10.0.0.25, 01:17:13, GigabitEthernet0/1
A2#
A2#show ipv6 route isis
IPv6 Routing Table - default - 5 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
RL - RPL, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
la - LISP alt, lr - LISP site-registrations, ld - LISP dyn-eid
lA - LISP away, a - Application
I1 ::/0 [115/10]
via FE80::F816:3EFF:FE0E:70D3, GigabitEthernet0/1
A2#
For both IPv4 and IPv6, there is default route, router A2 should be able to ping some destinations in other L1 areas:
A2#ping 192.168.0.8
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/6/8 ms
A2#ping 2001:DB8:b:0:1::d
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:B:0:1::D, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/11/37 ms
A2#
The same goes for router A3 and A4, they also should be able to ping remote IP addresses of other L1 areas in the topology.
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