Troubleshooting 1 - No routes

Load isis.tshoot1.cfg

#IOS-XE
config replace flash:isis.tshoot1.cfg

#IOS-XR
configure
load bootflash:isis.tshoot1.cfg
commit replace
y

R1 and XR2 have no ISIS routes in the routing table. Fix the issue without disabling any features that have been enabled on any other routers. You may only configure two routers.

Answer

#R2
router isis
 metric-style transition

#XR1
router isis 1
 add ipv4
  metric-style transition

Explanation

Before making any changes, we see that R1 and XR2 have no ISIS routes in the RIB:

If we look at the topology on R1 and XR2, we can see that all routers have ** for the metric. This indicates a metric-style mismatch:

If we do this on all routers, we see that only R1, R2, XR1, and XR2 have ** for all routers in the topology.

Next we can use show isis protocol on all routers to verify what metric-style all routers are using. We see that all routers are generating and accepting narrow metrics, except for R2 and XRv1:

To fix this, we must not disable wide metrics on R2 or XRv1, as that would be disabling a feature which goes against the instructions. (”Fix the issue without disabling any features that have been enabled on any other routers.”) We can configure both routers to generate and accept both narrow and wide metrics. We do this by setting the metric-style to transition.

#R2
router isis
 metric-style transition

#XRv1
router isis 1
 add ipv4
  metric-style transition 

Now R2 and XRv1 are accepting narrow metrics, as well as generating them:

Check the RIB on R1 and XRv2. They should now have full routes again:

Check the ISIS topology table as well. Now that R2 and XRv1 are generating narrow metrics in addition to wide, the other narrow-only routers can probably build the topology.

Note that there are five metric-style combination possibilities:

• narrow only (the default)

• wide metrics only (metric-style wide)

• transition - both wide and narrow are generated and accepted (metric-style transition)

• generate narrow only, accept both (metric-style narrow transition)

• generate wide only, accept both (metric-style wide transition)

metric-style wide transition is not a valid solution, as the routers will not generate narrow metrics for all other routers to use. Additionally, metric-style narrow transition is not a valid solution, as it disables the generation of wide metrics, which we could consider breaking the lab task instructions to not disable any features.