IS-IS Lab 5 Modify the Router Type

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Download Lab: VIRL | EVE-NG | GNS3


Image requirements:
 Cisco IOSv (vios-adventerprisek9-m.vmdk.SPA.156-2.T)


Introduction:
In this lab, you will configure IS-IS routers to belong to specific IS-type, either L1 only or L1/L2. There are two IS-IS areas in this topology, A100, and B200. Routers who are internal to the area should be configured as L1 IS-Type only, those nodes who stitch two areas together will be configured as L1/L2 routers. Adjacencies between nodes will be hardcoded to L1 or L2. 


Nodes Access: 
Enable:       cisco 
Username:  cisco 
Password:   cisco  



Topology:

Lab Tasks:

1. Within the A100 area, internal routers A1 and A3 should be IS-type L1 only, router A2 will act as L1/L2 IS-type since it will connect two areas together. 

2.  Within the B200 area, internal routers B2 and B3 should be IS-type L1 only, router B1 will act as L1/L2 IS-type since it will connect two areas together. 

3. In both areas, A100 and B200 IS-IS nodes' interfaces connected to the broadcast segments will be configured as L1 circuit-type, it will ensure that only L1 adjacencies will be formed. 

4. The link between A2 and B1 routers is the border between areas and only L2 adjacency has to be established over this connection. L2 circuit-type applied here. 


Lab procedure:

Step1: Configure router A1, change IS-type to L2 in the global router configuration mode, with is-type level-1 command. Under the G0/1 interface configuration mode change the circuit-type to the L1 with isis circuit-type level-1 command, this will put the interface to form only L1 adjacencies.
!
Configuration example:
!
A1(config)#router isis
A1(config-router)#is-type level-1
A1(config-router)#exit

!
A1(config)#interface g0/1
A1(config-if)#isis circuit-type level-1
A1(config-if)#end
A1#

!
Verify that router A1 is forming only L1 neighborship with its peers A2 and A3 with show isis neighbors command, you only should see L1 adjacencies have formed. 
!
A1# show isis neighbors 
System Id       Type Interface     IP Address      State Holdtime Circuit Id
A2              L1   Gi0/1         10.0.0.2        UP    22       A1.01             
A3              L1   Gi0/1         10.0.0.3        UP    24       A1.01

!
To check the circuit-type on the interface use this command: 

!
A1#show  clns interface  g0/1
GigabitEthernet0/1 is up, line protocol is up
  Checksums enabled, MTU 1497, Encapsulation SAP
  ERPDUs enabled, min. interval 10 msec.
  CLNS fast switching disabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 7 seconds
  Routing Protocol: IS-IS
    Circuit Type: level-1
    Interface number 0x1, local circuit ID 0x1
    Level-1 Metric: 1, Priority: 64, Circuit ID: A1.01
    DR ID: A1.01
    Level-1 IPv6 Metric: 10
    Number of active level-1 adjacencies: 2
    Next IS-IS LAN Level-1 Hello in 448 milliseconds  

!
As you can see from the output the IS-IS interface is level-1 type. 


Step2: Configure router A3 the same way as router A1, apply all configuration and verification commands you used in step 1. 


Step3: Configure router A2, despite the default behavior of the IS-IS router, the L1/L2 IS-type has configured, for the sake of the learning, hardcode this IS-type with command is-type level-1-2. Then configure the G0/1 interface to be L1 circuit-type. Also, the interface facing B2 has to be configured as L2 circuit-type only. 
!
The configuration example of setting the L2 circuit-type:
!
A2(config-if)#int g0/2
A2(config-if)#isis circuit-type level-2
A2(config-if)#end

!
Verify the state of IS-IS router with show isis protocol command: 
!
A2# show isis protocol
IS-IS Router: <Null Tag>
  System Id: 1921.6800.0003.00  IS-Type: level-1-2




  Manual area address(es):
        49.a100
  Routing for area address(es):
        49.a100
  Interfaces supported by IS-IS:
        GigabitEthernet0/2 - IP
        GigabitEthernet0/1 - IP
        Loopback0 - IP
  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



Check if interfaces G0/1 and G0/2 are in their respective circuit-type configurations with show clns interface command. 
!
A2# show clns interface G0/2
 GigabitEthernet0/2 is up, line protocol is up
  Checksums enabled, MTU 1497, Encapsulation SAP
  ERPDUs enabled, min. interval 10 msec.
  CLNS fast switching disabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 0 seconds
  Routing Protocol: IS-IS
    Circuit Type: level-2
    Interface number 0x2, local circuit ID 0x2
    Level-2 Metric: 10, Priority: 64, Circuit ID: A2.02
    DR ID: A2.02
    Level-2 IPv6 Metric: 10
    Number of active level-2 adjacencies: 1
    Next IS-IS LAN Level-2 Hello in 1 seconds



Step4: Configure internal routers B2 and B3 the same way as routers A1 and A3. Implement all appropriate configuration and verification commands. 


Step5: Finalize your IS-IS Lab by implementing the mirror configuration on the router B1. It has to be set to IS-type L1/L2 and circuit-type for the G0/2 interface is L2 and the G0/1 interface is L1. 

Step6: Confirm proper implementation of IS-IS across the entire topology and save the running-config. Ensure that connectivity occurs between internal routers in each area. Examine the IS-IS database and IP routing table. 

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