Re: Confussion over multi-homing

[Brantley Jones <bjones () redundant net>]

At 01:23 PM 9/14/2000 -0500, you wrote:

> Wouldn't one of the ISPs have to advertise a longer prefix?   I would think
> that the address space would come from only one of the providers, in which
> case the other provider would have to advertise this space on top of its own
> /20.  It is irrelevant whether the two ISPs advertise one another, the
> longer prefix would be the first choice for the backbone traffic.  If the
> longer prefix route goes down, traffic would still go to the /20 the other
> provider is advertising.
> The ISP who is advertising the route on top of its own /20 can't aggregate
> said route as it only can route to that portion of the address space defined
> in the longer prefix.
>
> Geoff Zinderdine

The problem is GETTING a /20 from anybody.  We recently tried and could 
only get a /23 (being a small start-up).  BUT, that /23 is (apparently) 
globally routable because of peering agreements with L3 and UUNET.  Our /23 
prefix has yet to be filtered by anybody.

Brantley