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" <[EMAIL PROTECTED]>
To: "Alex Haan"
<[EMAIL PROTECTED]>,<[EMAIL PROTECTED]>,<[EMAIL PROTECTED]>,<[email protected]>
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:[EMAIL PROTECTED]
Sent: terça-feira, 3 de Julho de 2007 19:59
To: Gustavo Novais; [EMAIL PROTECTED]; [EMAIL PROTECTED];
[email protected]
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" <[EMAIL PROTECTED]>
>To: "Paul Stewart" <[EMAIL PROTECTED]>,"Joseph Jackson"
><[EMAIL PROTECTED]>,"Alex Haan"
><[EMAIL PROTECTED]>,<[email protected]>
>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: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED] On Behalf Of Paul Stewart
>Sent: terça-feira, 3 de Julho de 2007 18:45
>To: 'Joseph Jackson'; 'Alex Haan'; [email protected]
>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: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED] On Behalf Of Joseph Jackson
>Sent: Tuesday, July 03, 2007 1:39 PM
>To: Alex Haan; [email protected]
>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: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Alex Haan
> > Sent: Tuesday, July 03, 2007 10:34 AM
> > To: [email protected]
> > 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
> >
> > _________________________________________________________________
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