[c-nsp] Configure two AS on one BGP router - Dynamic IP detecte

[Alex Haan]

Yeap, this is exactly for migration purposes due to upcoming merge event. 
Both AS numbers are likely to stay for some time. Currently, each AS has two 
BGP routers running IBGP and they work fine.

Let's say the origianal configurations are as follows:

Router A:
router bgp 12345
network a1.a2.a3.a4
neighbor x.x.x.x remote-as ABC

Router B:
router bgp 6789
network b1.b2.b3.b4
neighbor y.y.y.y remote-as ABC

I am trying to configure 2nd AS on router A. Does the suggested 
configuration look like this?

Router A:
router bgp 12345
network a1.a2.a3.a4
network b1.b2.b3.b4
neighbor x.x.x.x locate-as 6789 [no-prepend]

a1.a2.a3.a4 belongs to AS A and b1.b2.b3.b4 belongs to AS B. In this case, I 
either have to advertise networks from both AS through AS 6789 (I am not 
sure whether it works practically because ISPs sometimes filter the 
advertisement of the networks that do not belong to your AS) or suppress 
prefix a1.a2.a3.a4 as it belongs to AS 12345, am I right?

One alternative might be getting another neighbor IP address from ISP ABC, 
but I am not sure if the idea works practically. There are some other 
interesting things behind this scenario, such as peer connections 
within/between AS A and B because one router will be in both ASes.

Thanks,

Alex

>From: "Gustavo Novais" <gustavo.novais at novabase.pt>
>To: "Alex Haan" 
><alexshang123 at hotmail.com>,<paul at paulstewart.org>,<JJackson at aninetworks.com>,<cisco-nsp at puck.nether.net>
>Subject: RE: [SPAM] - RE: [c-nsp] Configure two AS on one BGP router - 
>Dynamic IP detected dnsbl.sorbs.net
>Date: Tue, 3 Jul 2007 20:40:14 +0100
>
>You have the option to suppress your actual AS from the AS path 
>(no-prepend), or not.
>
>By default your AS path will look like {local-AS your AS}.
>This will not suppress any routes, it is supposedly used for migration 
>purposes, (for example, two companies have merged and wish to keep their 
>peering agreements).
>
>To the peers of AS A, route X will appear as coming from A, and to the 
>peers of AS B, route X will appear as coming from B.
>If you want to filter anything, use filter-list|prefix-list|route-map 
>etc...
>
>Gustavo Novais
>
>
>
>
>-----Original Message-----
>From: Alex Haan [mailto:alexshang123 at hotmail.com]
>Sent: terça-feira, 3 de Julho de 2007 19:59
>To: Gustavo Novais; paul at paulstewart.org; JJackson at aninetworks.com; 
>cisco-nsp at puck.nether.net
>Subject: [SPAM] - RE: [c-nsp] Configure two AS on one BGP router - Dynamic 
>IP detected dnsbl.sorbs.net
>
>I guess that this enables advertisement of one AS's network while
>suppressing the advertisement of the networks from the other AS, right? One
>newb question, can I advertize the networks for both AS through one AS?
>
>Thanks,
>
>Alex
>
> >From: "Gustavo Novais" <gustavo.novais at novabase.pt>
> >To: "Paul Stewart" <paul at paulstewart.org>,"Joseph Jackson"
> ><JJackson at aninetworks.com>,"Alex Haan"
> ><alexshang123 at hotmail.com>,<cisco-nsp at puck.nether.net>
> >Subject: RE: [c-nsp] Configure two AS on one BGP router
> >Date: Tue, 3 Jul 2007 19:39:03 +0100
> >
> >You can also look at neighbor X.X.X.X local-as, to impersonate other AS's
> >
> >Gustavo Novais
> >
> >
> >
> >
> >-----Original Message-----
> >From: cisco-nsp-bounces at puck.nether.net
> >[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Paul Stewart
> >Sent: terça-feira, 3 de Julho de 2007 18:45
> >To: 'Joseph Jackson'; 'Alex Haan'; cisco-nsp at puck.nether.net
> >Subject: Re: [c-nsp] Configure two AS on one BGP router
> >
> >Never done it...
> >
> >But can you not create:
> >
> >router bgp 12345
> >network x.x.x.x
> >etc...
> >
> >router bgp 98765
> >network x.x.x.x
> >
> >into the same router??
> >
> >Paul
> >
> >
> >-----Original Message-----
> >From: cisco-nsp-bounces at puck.nether.net
> >[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Joseph Jackson
> >Sent: Tuesday, July 03, 2007 1:39 PM
> >To: Alex Haan; cisco-nsp at puck.nether.net
> >Subject: Re: [c-nsp] Configure two AS on one BGP router
> >
> >You could do it inside a VRF,  but I don't know if it would work for what
> >you want since it makes seprate routing tables.
> >
> > > -----Original Message-----
> > > From: cisco-nsp-bounces at puck.nether.net
> > > [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Alex Haan
> > > Sent: Tuesday, July 03, 2007 10:34 AM
> > > To: cisco-nsp at puck.nether.net
> > > Subject: [c-nsp] Configure two AS on one BGP router
> > >
> > > Hi Everyone,
> > >
> > > Is it possible to configure two ASes on one BGP router? If it's
> > > possible, how many feeds we are going to receive from an ISP peer? One
> > > or Two?
> > >
> > > Thanks,
> > >
> > > Alex
> > >
> > > _________________________________________________________________
> > > Tell us your tech love story in the Summer Lovin Competition for your
> > > chance to win laptop loaded with Windows Vista, Office 2007 and
> > > Windows Live OneCare.
> > > http://www.microsoft.com/canada/home/contests/summerlovin/default.aspx
> > >
> > > _______________________________________________
> > > cisco-nsp mailing list  cisco-nsp at 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 at 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 at puck.nether.net
> >https://puck.nether.net/mailman/listinfo/cisco-nsp
> >archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>_________________________________________________________________
>Windows Live Hotmail. Even hotter than before. Get a better look now.
>www.newhotmail.ca?icid=WLHMENCA148
>

_________________________________________________________________
http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_pcmag_0507