[c-nsp] primary & backup b/w w/ OSPF & BGP

[Adam Greene]

> Are your two uplinks connected to the same edge router?  If so, the
> simplest way to do this would be to apply route-maps on your outbound
> BGP announcements to prepend hops for the correct announcements and use
> policy routing to direct traffic to the right next-hop (if it is up).
> That way, you would get rid of the extra complications of having two
> OSPF areas.

Nope. We have two edge routers, one facing ISP A and the other facing ISP B.

> Also, how big are your announcements?  If you are announcing to two
> different ISPs, say /24 to each, your routes will most likely be
> filtered at some point, which would mean that part of your inbound
> traffic would go the "wrong" way.

At the moment, we have a /24 from ISP A, and (2) /22's allocated to us by
ARIN. We've had to send some local prefs with our route announcements to get
our two upstreams to make the correct routing choices (IIRC, UUNet has a
lower default local pref which tends to confuse the interaction a bit). We
are considering trying to announce a couple /24's of one of the /22's
separately, but I am concerned about the filtering as you say.
Interestingly, Verio seems to accept /24 announcements now (I understand
they have traditionally had one of the most conservative filtering
policies): http://info.us.bb.verio.net/routing.html#PeerFilter

Adam

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