CCNP Finally!

This hasn't been an entirely easy certification to obtain. Although it does seem as though it were unattainable at times. Not that I thought the path to be super challenging, but that the opportunities to go forward with the certification never lined up. As of the official email from Cisco, I am now a CCNP …


Moving to Joomla

As my interests change and my career moves forward, I have more of a need to be in control of my own content. For that reason, and for fun, I have decided to build and host my own blog site. It is temporary now but I hope to have everything moved over pretty quickly. This …


So I got a little sidetracked and decided to pursue a relevant certification. Since I had obtained my CCNP, I thought it logical to get a design cert. So I took a class and then the exam and passed. Now I hold a CCDA certification. The exam wasn't too bad, although it was one if …


Good write-up. As a service provider engineer, I try to keep up on the latest technologies. Having just tested again for ROUTE, I see that they are throwing EVPN into the questions. However, they usually tend to explain it from the customer perspective.


This blog introduces PBB-EVPN over an MPLS network. But rather than just describe the technology from scratch, I have tried to structure the explanation assuming the reading is familiar with plain old MPLS L3VPN and is new to PBB and/or EVPN. This was certainly the case with me when I first studied this topic and I’m hoping others in a similar position will find this approach insightful.

I won’t be exploring a specifc quirk or scenario – rather I will look at EVPN followed by PBB, giving analogies and comparisons to MPLS L3VPN as I go, before combining them into PBB-EVPN. I will focus on how traffic is identified, learned and forwarded in each section.

So what is PBB-EVPN? Well, besides being hard to say 3 times fast, it is essentially an L2VPN technology. It enables a Layer 2 bridge domain to be stretched across a Service Provider core while…

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Ongoing documentation for Cisco devices

===================================== Common Cisco 7600 T-Shoot commands ===================================== telnet A.B.C.D [port3] /vrf [name] /source-interface [interface] clear ip bgp A.B.C.D vrf [name] soft show ip bgp vpnv4 vrf [name] neighbors A.B.C.D routes show ip bgp vpnv4 vrf [name] neighbors A.B.C.D advertised-routes show ip bgp vpnv4 vrf [name] neighbors A.B.C.D received-routes show vlan internal usage sh ip community-list …

Asymmetric routing caused by unfiltered redistribution

Good lab write up on routing distribution and using EEM scripts.


This quirk demonstrates how the different administrative distances of BGP, combined with the Best Path Selection algorithm can cause asymmetric routing if redistribution isn’t done carefully.

As a reminder, each blog will follow 3 sections: The quirk, the search and the work. The quirk describes the problem, the search shows how a solution was reached and the work shows the technical and CLI aspects.

The quirk

The scenario we will be looking at is as follows:


The network consists of an MPLS core with multiple remote sites (only one is shown here). There is a dual homed breakout site, which passes through a firewall (performing security and address translation services as normal) and onwards to an internet facing WAN connection.

A default route is learned over eBGP from the Provider Edge router (PE4) connected to the internet facing Customer Edge router (CE4). This is redistributed into OSPF. The MPLS facing…

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