Hi all I have a question:
I see very few prefixes in a routing table and combining the prefixes
does not cover addresses space, for example, {78.41.184.0/21,
91.103.239.0/24, 91.103.232.0/22, 82.138.64.0/23, 91.103.232.0/21,
77.95.71.0/24} are all prefixes I observed from a BGP speaking router,
I am just asking is this router using a default routing for all the
other destinations?
Thanks a lot
If it has a default route, 0.0.0.0/0, in its routing table, then yes, it is.
If it does not, then no, it is not.
-jasper
Date: Mon, 5 Jan 2009 18:05:48 -0600
From: Kai Chen
is this router using a default routing for all the other
destinations?
Either that:
> sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
or partial tables with no default:
> sh ip route 0.0.0.0
% Network not in table
is what you'd expect.
Eddy
Will this default route 0.0.0.0/0 be exporting to AS-level neighbors?
Sorry I have question
Why it needs default routes when running BGP?
Thank you
Will this default route 0.0.0.0/0 be exporting to AS-level neighbors?
Date: Mon, 5 Jan 2009 21:52:12 -0600
From: Kai Chen
Will this default route 0.0.0.0/0 be exporting to AS-level
neighbors?
You can have it exported, or you can have it not exported. It depends
how the route is known (eBGP? OSPF? static?) and what you set BGP to
redistribute.
Eddy
Date: Tue, 6 Jan 2009 07:40:16 -0500 (EST)
From: chloe K
Why it needs default routes when running BGP?
If you have a full table, you do not need default. It's even desirable
to drop road-to-nowhere packets inside your network, before they clog up
your connections.
However, consider that you may encounter some problems -- such as
insufficient RAM to deal with growing table size -- that leave you
forced to take a partial table. Then what?
If you're running BGP, you probably have more than one upstream, so you
don't want static defaults (unless the next hop is a serial interface).
To deal with this, you can have your providers originate default _and_
send a full table.
Under normal circumstances, use a route map that nukes 0/0. If you find
yourself in a jam, replace the route map with one that allows 0/0 and
discard long paths, AS_PATHs that you consider troublesome, et cetera.
You still have the benefit of directing certain routes to a specific
provider, but with a smaller (partial) table.
Finally, note that not every router needs full tables. Consider a
peering router that exchanges traffic between a network's peers and
customers.
Eddy