IS-IS Lab 11 Transition to wide metric

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Download Lab: VIRL | EVE-NG | GNS3


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


Introduction: 
This lab is similar to the second part of the previous lab "IS-IS metric" but here you will practice how to go from narrow metric to the wide metric without corrupting the IS-IS database and potentially disrupting the data flow over the link-state domain. If your IS-IS implementation for some reason has been configured with a narrow metric and now you need to switch to a wide metric, perhaps, there is the requirement to enable IPv6 support in your topology, here you will learn how to do this seamlessly. Transition metric-style is the feature you configured in the IS-IS router configuration to enable both the Narrow and Wide metrics while switching to the Wide metric only. Doing this way allows you to smoothly go from old short metric to the new long, preventing you from causing database instability and breaking connectivity. 


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


Lab tasks: 

1. Determine the current configuration of metric style on the routers in the topology. 

2. Configure metric transition on all router in the topology. 

3. Verify that both the Narrow and  Wide metrics are enabled. 

4. Enable only the Wide metric on all routers in the topology. This will disable the Narrow metric. 

5. Verify that only the Wide metric is enabled. 


Lab procedures:


Step1: Begin this lab by checking IS-IS protocol parameters and database on the router A1. 

A1#show  isis protocol

IS-IS Router: <Null Tag>
  System Id: 1921.6800.0001.00  IS-Type: level-1
  Manual area address(es):
        49.a100
  Routing for area address(es):
        49.a100
  Interfaces supported by IS-IS:
        GigabitEthernet0/1 - IP
        Loopback172 - IP
        Loopback0 - IP
  Redistribute:
    static (on by default)
  Distance for L2 CLNS routes: 110
  RRR level: none
  Generate narrow metrics: level-1-2
  Accept narrow metrics:   level-1-2
   Generate wide metrics:   none
  Accept wide metrics:     none

 Now only a narrow metric is enabled. 

A1#show  isis database detail A1.00-00
IS-IS Level-1 LSP A1.00-00
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime/Rcvd      ATT/P/OL
A1.00-00            * 0x00000006   0x7A17                 847/*         0/0/0
  Area Address: 49.a100
  NLPID:        0xCC
  Hostname: A1
  Metric: 1          IS A3.01
  IP Address:   192.168.0.1
  Metric: 1          IP 10.0.0.0 255.255.0.0
  Metric: 10         IP 172.16.0.0 255.255.255.0
  Metric: 10         IP 172.16.1.0 255.255.255.0
  Metric: 10         IP 172.16.2.0 255.255.255.0
  Metric: 10         IP 172.16.3.0 255.255.255.0
  Metric: 10         IP 172.16.4.0 255.255.255.0
  Metric: 10         IP 172.16.5.0 255.255.255.0
  Metric: 10         IP 172.16.6.0 255.255.255.0
  Metric: 10         IP 172.16.7.0 255.255.255.0
  Metric: 10         IP 192.168.0.1 255.255.255.255
  

Step2: Enter the IS-IS router configuration mode of router A1 then configure metric-style transition.  

A1(config)#router  isis
A1(config-router)#metric-style transition 


Step3: Observe the changes to the output of show isis protocol and database. 

A1#show  isis protocol 
IS-IS Router: <Null Tag>
  System Id: 1921.6800.0001.00  IS-Type: level-1
  Manual area address(es):
        49.a100
  Routing for area address(es):
        49.a100
  Interfaces supported by IS-IS:
        GigabitEthernet0/1 - IP
        Loopback172 - IP
        Loopback0 - IP
  Redistribute:
    static (on by default)
  Distance for L2 CLNS routes: 110
  RRR level: none
  Generate narrow metrics: level-1-2
  Accept narrow metrics:   level-1-2
  Generate wide metrics:   level-1-2
  Accept wide metrics:     level-1-2

IS-IS supports both metric styles. 

A1#show  isis database detail A1.00-00IS-IS Level-1 LSP A1.00-00
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime/Rcvd      ATT/P/OL
A1.00-00            * 0x00000008   0xEF20                1013/*         0/0/0
  Area Address: 49.a100
  NLPID:        0xCC
  Hostname: A1
  Metric: 1          IS A3.01
  Metric: 1          IS-Extended A3.01
  IP Address:   192.168.0.1
  Metric: 1          IP 10.0.0.0 255.255.0.0
  Metric: 10         IP 172.16.0.0 255.255.255.0
  Metric: 10         IP 172.16.1.0 255.255.255.0
  Metric: 10         IP 172.16.2.0 255.255.255.0
  Metric: 10         IP 172.16.3.0 255.255.255.0
  Metric: 10         IP 172.16.4.0 255.255.255.0
  Metric: 10         IP 172.16.5.0 255.255.255.0
  Metric: 10         IP 172.16.6.0 255.255.255.0
  Metric: 10         IP 172.16.7.0 255.255.255.0
  Metric: 10         IP 192.168.0.1 255.255.255.255
  Metric: 1          IP 10.0.0.0/16
  Metric: 10         IP 172.16.0.0/24
  Metric: 10         IP 172.16.1.0/24
  Metric: 10         IP 172.16.2.0/24
  Metric: 10         IP 172.16.3.0/24
  Metric: 10         IP 172.16.4.0/24
  Metric: 10         IP 172.16.5.0/24
  Metric: 10         IP 172.16.6.0/24
  Metric: 10         IP 172.16.7.0/24
  Metric: 10         IP 192.168.0.1/32

In the output, there are two identical sets of subnets, one with the subnet mask and another is with prefix notation. This is the indication of both styles of metrics are running. The narrow metric in the database represents subnets with a mask, while wide metric with prefixes.


Step4: Repeat steps 1 through 3 on the rest of the IS-IS nodes in the topology. 
Then start from Router A1 begin to enable wide metric only. 

Configuration Example: 
 !
A1(config)#router  isis
A1(config-router)#metric-style wide  


Step5: Confirm that the Wide metric has been implemented across the entire topology. 


Topology: