BGP

In this post I will be showing you how its possible to use different paths between your PE routers on a per VRF basis.

This is very useful if you have customers you want to “steer” away from your normal traffic flow between PE routers.

In this post i would like to explain how you can fix a multicast RPF failure using BGP.

If you take a look at the topology in figure 1, we have a network running EIGRP as the IGP

and where R1 advertises its loopback 0 (1.1.1.1/32). R4 also has a loopback 0 with the 4.4.4.4/32 address.

A a couple links that you guys mind find good:

[http://prakashkalsaria.files.wordpress.com/2010/06/pe-ce.jpg

]1 http://lovemytool.blip.tv/posts?view=archive&nsfw=dc

First one is a great overview of some BGP options.

The second one is a page with a list of videos of Sharkfest. All things wireshark it would appear 🙂

I have a few minutes this morning that i want to use to clarify a special BGP feature which i had misunderstood until a few days ago.

This has to do with the aggregate-address that you use to create a summary address. One of its many options includes the “advertise-map” parameter.

In my continued quest through BGP i ran into a couple of things which i wanted to share my thoughts about.

All of them has to do with a non-direct peering between BGP peers.

Originally the BGP protocol was designed to be run between directly connected routers. Then came along these busy times where we might want to have two connections, for redundancy and load-balacing purposes. We also want to have a single peering only. These days we might even have non-BGP speakers in our core, such as with MPLS.

I want to point your attention to a great article right here: ardenpackeer.com, good stuff, deffinately worth the read.

I am looking this up today, as i ran into it last night doing more BGP labs. Again, just to re-iterate. The feature gives you the ability of taking a network, thats advertised by a certain source, and inject a more specific route of this network into the BGP table (and then to the routing table). When will this be used? For aggregation purposes.

More Narbik Labs. I have arrived at the BGP section, and its very good. It touches on some more obscure features that are really useful.

One of the things i ran into was the use of advertise-maps, exist-maps and non-exist maps. I have used these before, but very briefly.

So yesterday I setup a BGP scenario which you can see below:

I am doing mutual redistribution on both R1 and R3, between BGP and EIGRP.

I am advertising a couple of routes from R4 (AS 65001) to R1 (AS 65000).