LDP Inbound Label Advertisement Filtering
Load isis.cfg
Configure LDP using LDP autoconfig under ISIS
Configure inbound label filtering on R1 and XR2 to filter out label bindings received from their LDP neighbors for all transit prefixes
Answer
Explanation
Inbound LDP advertisement filtering is much easier to configure than outbound advertisement filtering. In both IOS-XE and IOS-XR, we must apply an ACL on a per-neighbor basis to filter incoming LDP bindings.
On IOS-XE, we use the following command:
On IOS-XR, we use the following command:
Verification
On R1, since R2 is the only LDP peer, we can look at the LDP bindings summary for a quick check that the inbound filtering is working. Before implementing the filter, we see that we have one remote binding for every prefix:
After implementing the filter, we should only see a remote binding for the /32 loopbacks, due to our standard ACL we are applying for R2:
Likewise, on XR2, we can use the same command. First we verify that we are receiving one remote label (from XR1) for every prefix:
Next, we apply the inbound filter and verify that XR2 has discarded XR1’s bindings for non-loopback prefixes:
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