Re: BGP and aggregation

[Scott Granados <scott () graphidelix net>]

-
This is a great solution to a point.  I did this, with the help of 
someone who reads this list frequently:) but you have to jump through 
some hoops should you wish both cities to reach each other.  Assuming 
for example all your dns and mail servers are in one city you'd have to 
jump through this hoop.  

On Sat, 11 May 2002, Richard A Steenbergen wrote:

> On Sat, May 11, 2002 at 05:34:39PM -0400, 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)
>
> If I was paying for transit, I would want THEM to do the work of 
> delivering it to the right city, without wasting the bandwidth of my 
> circuit (unless they're really close and that circuit is really cheap).
>
> If you're using the same transit provider in both cities, how about
> announcing the /20, and the 2 /21s tagged with no-export. The /20 would be
> heard by the world and get the traffic to your transit provider, then the
> /21s would route it to the right exit point.