> Does anyone know if and how Juniper implements something similar to Cisco's
> BGP Conditional Advertisements. Cisco's Conditional advertisement is
> useful in a multihomed network, in which some prefixes are to be advertised
> to one of the providers, only if information from the other provider is
> missing. This condition would indicate a failure in the peering session, or
> partial reachability. So, basically routes are advertised only if other
> routes disappear from table.
I didn't see an actual answer to this question so let me try.
I don't know of anything in our routing policy that would provide
the exact same functionality as cisco's conditional advertisement.
However you may be able to achieve what you are looking for by
using static routes with the resolve keyword.
For example, if the prefix you wish to advertise is 3/8 you
could configure:
routing-options {
static {
route 3.0.0.0/8 {
next-hop x.x.x.x;
resolve;
}
}
}
where x.x.x.x is an IP address that is chosen out of the address space
that is advertised by one of the two providers. (Perhaps x.x.x.x is
an address from your link to the provider, or maybe it is a more
specific than one of the prefixes you expect to learn from this
provider.)
Lets assume that you also learn of 3/8 via BGP, and export that
prefix to the backup provider via the policy:
from {
protocol bgp;
route-filter 3.0.0.0/8 exact;
}
then accept;
When the static route is active, you'll wind up not advertising the
prefix since the protocol match fails. When the x.x.x.x address
is missing, the static route goes inactive, and you advertise 3/8
due to the protocol matching.
Depending upon what you want in your RIB and FIB, you might want
to get more complicated, perhaps writing an export policy that matches
on the next-hop instead.
This archive was generated by hypermail 2b29 : Mon Aug 05 2002 - 10:42:35 EDT