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bgp

Well, Now What?

September 29, 2010

At the end of July I passed the Cisco Building Scalable Cisco Internetworks (BSCI) examination, the last of four to earn the Cisco Certified Network Professional (CCNP) certification. I recently found myself wondering, “Well, now what?” A year ago, if you asked me what my plans were after completing the CCNP the obvious answer would […]

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Getting BGP routes into dynamips (with video)

August 21, 2009

UPDATE: If you’re not interesting in doing this yourself and just want to see it in action, check out the video, “Dumping 265k BGP routes into dynamips”. When I went through these steps to document, I ended up with 298,870 prefixes in my dynamips router. When I did it the second time, to record the […]

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Using BGP communities to influence routing, part 2

August 10, 2009

I wanted to write a follow-up to a couple of earlier posts, Using BGP communities to influence routing and Allowing customers to manipulate routing using BGP communities to show some more ways we can use BGP communities to influence routing on the Internet. What we’re going to see today is very common in the real world, […]

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Dynamips, a 7200, and a full BGP table

August 7, 2009

I’ve been using dynamips on and off for a while now and always knew it was cool as hell, but this just really impressed me: c7200# show ip bgp summary BGP router identifier 192.168.1.201, local AS number 65101 BGP table version is 593019, main routing table version 593019 297882 network entries using 34852194 bytes of […]

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Configuring BGP maximum-prefix

July 21, 2009

The “maximum-prefix” feature of BGP lets us dictate how many prefixes an individual neighbor can send to us. Imagine that we have a private peering with another organization and that organization is only advertising to us their own networks (and not the global BGP tables). While talking with the other organization, we’ve found out that […]

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Using BGP’s MED to influence inbound routing

July 20, 2009

If you remember how BGP’s best path selection algorithm works, you’ll likely remember hearing about the multi-exit discriminator, or MED. The MED is an optional, non-transitive attribute of BGP. When we have multiple entry points (connections) to another AS, this allows us to tell the other AS how we would like them to route traffic […]

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Configuring MD5 Authentication for BGP Peers

July 10, 2009

I got an e-mail recently from a reader who asked me about how to set up MD5 authentication between a pair of BGP peers, so I thought I’d do a quick write-up and example. Setting up MD5 authentication is really simple. For our example, we’ll use a pair of routers connected over their serial 0/0 […]

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BGP load sharing, dual-homed to one SP

March 22, 2009

Here’s another lab that I just made up using dynamips and dynagen. There is a download link to the .net file I used (modify it as needed) at the bottom of this post. NOTE: See the video demonstration below! For this lab, here’s the topology we’re working with:

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Allowing customers to manipulate routing using BGP communities

March 20, 2009

UPDATE: I made a video demonstration of this as well. You can find it at the bottom of this post. Let me know what you think! Thanks. Upon request, and as a sort of “continuation” of a prior post, “Using BGP communities to influence routing“, I’m going to demonstrate how to permit this to occur […]

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Using BGP communities to influence routing

March 18, 2009

Previously I’ve covered using weight, local preference, and AS path prepending to influence routing between autonomous systems running BGP. Today we’ll look at one of the common methods for influencing routing, and that is BGP community values. BGP communities are simply values attached to a route that is sent to BGP peers. This values have […]

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