L2 protocol tunelling (ASR920)

Sometimes when we purchase a L2 service from a service provider, we need to have our L2 protocols tunneled.

ASR920 platform gives the operator three option to choose from:

  • l2protocol tunnel
  • l2protool peer
  • l2protocol forward

Although I've been working with ASR920s for a while, I didn't have the time to …

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Constrained Route Distribution

I write this post as I go through Route Target Constraint (RFC 4364) feature. I'll try to answer below questions:

  • What problem does it solve?
  • How vendor support does look like?
  • What are deployment considerations?

Before looking into the feature, let's think for a moment how typical network involving route …

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IS-IS authentication

Here are my notes about how IS-IS deals with authentication. I'll be working on a simple network consisting of IOS XE, IOS XR and Junos based routers.

Here is reference diagram:

Reference lab diagram

Some initial checks

First, I'll start off by verifying IS-IS adjacencies on R6.

R6#sh isis neighbors

Tag 1 …
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BGP best path selection in MPLS/IP BGP VPNs

Recently a friend of mine asked a question which can be summarized as

does the Route Distinguisher of Route Target play any role in BGP best path selection in MPLS BGP VPNs?

I'll try to answer this question based on the following scenario:
Reference lab diagram
We have two PE routers running IOS …

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Service Provider multicast part 1 - Draft-Rosen mVPN

This is one of the oldest methods of implementing multicast in Service Providers core. Quite popular, but unfortunately has some serious limitations.

We will see the operation of Draft-Rosen deployment model in practice by building sample lab topology and looking how particular pieces of technology fit together. Let’s look …

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Notes on multicast - PIM Dense Mode


The shortest statement describing PIM-DM behavior is "flood and prune". We assume that every host on every network segment wants multicast traffic. Later routers can signal that they aren't interested anymore in receiving particular multicast group.

High level overview of PIM-DM operation is as follows:

  • Source starts sending multicast …
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