This list does tend to focus on public internet issues and forget that BGP is used in corporate or other "non-internet" environments that don't follow nice conventions and after 15+ years of corporate take-overs,mergers and demergers can often find situations where AS Paths need to be "cleaned"or manipulated with something more flexible than a straight pre-pend. IOS allows every other key BGP metric to be tweaked and we accept the risks that brings - so this sort of manipulation of the AS-Path is long overdue.
Examples where I have had to dump BGP routes into an IGP for a hop and stick them back into BGP with a "clean" AS-Path. :- A) 2 independant organisations both use MPLS VPN from the same provider and want to exchange routes across a private peering. The MPLS provider AS is in the AS-Path on both sides and the provider drops routes. The provider doesn't offer any of the provider side workarounds. B) 1 Organisation that has historically been a fully private network and has some historic peerings that use non-private AS/non-registered AS now wants to have a private peering with "a proper" public network. The AS-Path needs to have the "junk" removed before the routes could be advertised. Yes the historic networks should be migrated away but the fact is there is often no resource and no money to do that when the workaround is simply another Router. C) Organisation wants to Dual Home to 2 ISPs at 2 locations for a new internet service. It wants to use its private network for backhaul between the sites but can't have free flow of routes between because if they traverse the MPLS VPN they get the provider AS inserted in the path. I don't intend to debate the above....they happened and the solutions were ratified by Cisco but in all cases manipulating the AS-Path (usually to remove the MPLS provider public AS) would have been much much easier than the final solutions. The summary is...BGP isn't just used on the Internet, and corporate networks get messy when CEOs get ambitious (or fired). Dean -----Original Message----- From: cisco-nsp-boun...@puck.nether.net [mailto:cisco-nsp-boun...@puck.nether.net] On Behalf Of mas...@nexlinx.net.pk Sent: 28 May 2009 17:56 To: Varaillon Jean Christophe Cc: cisco-nsp@puck.nether.net Subject: Re: [c-nsp] Remove BGP AS path number number from an AS PATH yup, you can't remove public AS from AS path. would you please share the idea why you wana remove it :) there are many other attributes to tweak bgp, y not u use them. BR\\ Masood > I doubt that you can do that... but if this is to influence your outgoing > traffic, then I would use local-preferences. > > Christophe > > > -----Original Message----- > From: cisco-nsp-boun...@puck.nether.net > [mailto:cisco-nsp-boun...@puck.nether.net] On Behalf Of Michalis Palis > Sent: Thursday, May 28, 2009 9:49 AM > To: cisco-nsp@puck.nether.net > Subject: [c-nsp] Remove BGP AS path number number from an AS PATH > > Hello All > > Is their a way to remove the first AS number (not private) from an AS > path? > > For example we are receiving a route with AS PATH 123 456 456 456 and we > want to remove the 123 AS and put in the BGP table the route with AS 456 > 456 > 456 . > > Thanks for your reply > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > > > __________ Information from ESET Smart Security, version of virus > signature > database 4112 (20090528) __________ > > The message was checked by ESET Smart Security. > > http://www.eset.com > > > > __________ Information from ESET Smart Security, version of virus > signature > database 4112 (20090528) __________ > > The message was checked by ESET Smart Security. > > http://www.eset.com > > > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
