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Re: redistribute bgp considered harmful

  • From: Joe Abley
  • Date: Fri Oct 04 23:41:07 2002


On Friday, Oct 4, 2002, at 18:01 Canada/Eastern, Sean Donelan wrote:

Should the Service Provider version of routing software include the
redistribute bgp command?  Other than CCIE labs, I haven't seen a
real-world use for redistributing the BGP route table into any IGP.

If the command was removed (or included a Are your sure? question) what
would the affect be on ISPs, other than improving reliability by
stopping network engineers from fubaring a backbone?
Participants at the NZIX, the original exchange point in New Zealand hosted by the University of Waikato, used to exchange routes using OSPF. And BGP and RIP and IGRP. Those were the days.

In order to export our routes to other exchange participants, we redistributed BGP routes into a dedicated exchange OSPF process, and we had some careful redistribution going on in the other direction to harvest the NZIX routes into BGP for use within our AS.

The NZIX has been shut down for quite a while now, so this is not a reason for retaining the ability to commit such heinous crimes against nature. However, I do remember that a "redistribute bgp" under "router ospf" did precisely nothing on the IOS loads we were using at the time, unless there was also a "bgp redistribute-internal" command in the config.

So if this works the way I remember it working, it seems like there might already be an "are you sure" mechanism in place, in IOS at least. There are some words about this on CCO:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/ 121cgcr/ip_r/iprprt2/1rdbgp.htm#xtocid17

bgp redistribute-internal

To allow the redistribution of iBGP routes into an interior gateway protocol such as IS-IS or OSPF, use the bgp redistribute-internal command in router configuration mode. To remove the bgp redistribute-internal command from the configuration file and restore the system to its default condition where the software does not allow the redistribution of iBGP routes into Interior Gateway Protocols (IGPs), use the no form of this command.

Joe