FirstDigest » Cisco-EGP

Cisco: 2-Bytes / 4-Bytes ASN BGP scenarios

Calin — Thu, 17 Sep 2009 22:23:00 +0000

In my last post I wrote some basics about the new 4-bytes AS number which is supported on new Cisco IOS images. Now I would like to give you a brief overview about different BGP peering scenarios that you can meet in the real world. Even if the configuration examples in this article are on a Cisco hardware with the latest IOS, the BGP scenarios can be applied to any other platform.

OK, let take the following topology (the high [...]

4-bytes Autonomous System Number

Calin — Wed, 02 Sep 2009 18:16:43 +0000

Last week I received a form from APNIC with a new AS numbers. When I had a look through papers I saw there something strange: AS 123456 (I replaced the original with this number). 6 digits. First I thought that there is a mistake or something, then I recall the new 4-bytes ASN. If for IPv6 the things seems to be moving slower, than for the new format of AS numbers, it seems that the things are going faster. So faster that by January 1, [...]

Cisco: 6 best practice security tips for BGP

Calin — Thu, 05 Feb 2009 10:29:13 +0000

As we all know, in today’s digital communication world, there is a very big possibility that your network is or was target for a malicious activity. BGP is one of the most targeted routing protocols when we are talking about network attacks.Why? This is quite simple. BGP is your connection to the exterior world (peer networks, Internet and everything which is outside your LAN/MAN), so it is somehow normal to be the main target of the conducted attacks. If in case of the WWW, DNS, [...]

Cisco: BGP path selection for inbound traffic

Calin — Wed, 10 Dec 2008 21:25:18 +0000

In some previous post we saw how we can manipulate BGP paths using attributes for outgoing traffic. Today we will see how to use another BGP attribute, but this time for manipulating inbound traffic. First I would like to ask you to have a look into the topology file and also to check the config files (if you have a basic idea about how BGP is configured that you don’t need the config files).

From the [...]

Cisco: How to improve BGP table stability with route dampening

Calin — Tue, 02 Dec 2008 23:48:08 +0000

One of the issues that can affect BGP table stability is link flapping. Imagine that if a link to a network is flapping very often, BGP process has to remove the route to that network from the BGP table and implicit from the routing table and then we the link is available again to re-introduce the prefix in these tables. All this means some BGP operations that consume CPU and memory of the machine.

A way to improve the BGP table stability is to use [...]

Cisco: BGP path selection for outgoing traffic

Calin — Mon, 01 Dec 2008 12:28:37 +0000

Before going further on, please download the topology and the initial configuration files and have a close look into them (mostly into topology drawing). Also, this tutorial is addressed to people that know what is BGP and how to do a basic configuration for peering establishing.

For modifying the BGP automate selection of the best path, we have to modify some of BGP attributes from the table below:
Since today we will deal [...]