[c-nsp] BGP advertisements more specific than IGP

[Mack McBride]

You can use conditional advertisement to do what you are wanting to do.
But as Randy mentioned you should really use communities with your upstreams to influence traffic.
If communities don't work then consider conditional advertisement.
http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cbgp.html#wp9071
If you advertise your deaggregates you should still advertise your aggregate block.
That allows those of us who don't care about your traffic engineering desires  but
do care about the routing table size to drop your deaggregates.
At some point a lot of providers are going to be dropping deaggregates.

LR Mack McBride
Network Architect

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of James Urwiller
Sent: Thursday, February 28, 2013 8:12 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] BGP advertisements more specific than IGP

I have a BGP multi-homed invironment that I am having problems balancing inbound traffic, besides prepends which don't seem to be helping anymore, I have heard that announcing my networks more specifically could also influence inbound traffic.  My question is, for example... If I have a /23 that I am using as a /23 in OSPF, can I announce that in BGP more specifically (2, /24's)  without having to them break it up internally as well?  What I foresee happening is this..

Example:
BGP:
Network 192.168.0.0/24
Network 192.168.1.0/24

OSPF:
Network 192.168.0.0/23

I would think in this scenario, the IP addresses 192.168.1.0 and 192.168.0.255 would not have a route in BGP, even though they are valid addresses for use when used as a /23.  Since I would be multi-homed, I would still advertise the network as the aggregate /23 on the circuit I don't want to take as much traffic, so would those IP addresses in this scenario still work, but only through the circuit I advertise as the aggregate??

James Urwiller
Network Operations Manager
CCNA 11567125
American Broadband
402-426-6257 - Office
402-278-1875 - Cell
402-426-6273 - Fax
jurwiller at americanbb.com<mailto:jurwiller at americanbb.com>

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