BGP and aggregation
Scott Granados
scott at graphidelix.net
Sun May 12 21:02:35 UTC 2002
Actually I ran this way for a while as a primary. I had three sites
attached via cogent entirely all announcing a /19 and the internally a
/21 each and a couple /21's out of the primary location. In the main
location was a 7507 and in the two other pops 6509's. We set ospf
internally, set up bgp for the announcements at each site and used the
no-export tag for the more specifics. Then gre tunnels:) for the
internal. It worked and I pushed probably 45 to 50mb over the internal
loops or gre tunnels. Not ideal but it worked.
On Sun, 12 May 2002,
Stephen J. Wilcox wrote:
>
> Interesting point there Scott.. we were discussing just that at a recent
> IXP meeting I was at. Theres a number of different ways (well hacks) in
> which you can keep connectivity between two halves of an AS network in the
> event of a split.
>
> Is anyone out there actually doing something either this or similar to
> keep two halves connected in the event of a split.. and have you actually
> run successfully on your backup and maintained a reasonable throughput
> (say 30 or 40Mbs) ? I'd be interested if anyone has a proven technique as
> I want to implement something myself and dont really want to test it by
> pulling the plug on some backbone links and waiting to see what happens!
>
> Steve
>
> On Sun, 12 May 2002, Scott Granados wrote:
>
> >
> > Don't forget that if both sites use the same as even if the connection
> > link drops they will not be able to see each other over the upstream
> > provider as routers won't take the srutes from the same as. If this
> > isn't a problem don't worry about it. If you wish to preserve
> > connectivity between cities you should have a back-up link or use
> > different as's or gre tunnels:).
> >
> > On Sat, 11 May 2002, Ralph Doncaster
> > wrote:
> >
> > >
> > > I have transit in 2 cities. I have a circuit connecting the 2 cities as
> > > well. So far I've been using non-contiguous IPs, so there's been no
> > > opportunity for aggregation. Having just received my /20 from ARIN, I'm
> > > trying to plan my network. Lets say I split the /20 into 2 /21's, one for
> > > each city. I'd like to announce the aggregate /20 instead of 2 /21's, as
> > > long as the circuit connecting the 2 cities is working. If the circuit
> > > goes down I want each city to announce the local /21. Is this
> > > possible? (using either a Cisco router or Zebra)
> > >
> > > Ralph Doncaster
> > > principal, IStop.com
> > > div. of Doncaster Consulting Inc.
> > >
> >
> >
>
>
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