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Redistribution of OSPF Routes into BGP

Posted on 2013-06-25
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Last Modified: 2013-06-25
Hi Experts,

We have a small, three-site network, and we're migrating to an MPLS cloud for site connectivity. Starting at the internet and working in, each site will look like this:

Internet --> Internet Provider Router --> Firewall --> LAN Router --> MPLS Provider Router --> MPLS Cloud

The firewall and LAN router at each site participates in OSPF and is a part of area 0. Each site needs to redistribute their OSPF routes into BGP, and we are unfamiliar with how to do this.

Here is our OSPF config from one site/router:

router ospf 1
 log-adjacency-changes
 network 192.168.16.0 0.0.7.255 area 0
 network 192.168.50.0 0.0.0.255 area 0
 network 192.168.117.0 0.0.0.255 area 0

It seems that the only command to redistribute these routes into BGP is this:

router bgp 100
 redistribute ospf 1

Can someone please confirm if this is correct or if anything else is needed? Are there any other considerations?

Thanks!
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Question by:meade470
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4 Comments
 
LVL 29

Expert Comment

by:Jan Springer
ID: 39276356
Honestly, stability is better with BGP.

I would nail down the networks using a static route to null with a distance of 250 (if they're present in OSPF, the 110 will win) instead of redistributing OSPF into BGP.
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Author Comment

by:meade470
ID: 39276386
Thanks for the quick response. We're CCNA-like beginners with routing protocols. Could you elaborate on that a bit, please?
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LVL 29

Accepted Solution

by:
Jan Springer earned 2000 total points
ID: 39276398
ip route 192.168.0.0 255.255.255.0 null 0 250

router bgp 65535
 network 192.168.0.0 mask 255.255.255.0


For a subnet to be announced via BGP, it must be in the routing table via an interior routing protocol.  I don't like my BGP to churn and my prefixes to be dampened if possible and so I nail down the null routes and identify the network to be announced in BGP.

I usually take that a step further and use a prefix-list to identify what I would like to announce so that I am not announcing my eBGP neighbor's prefixes to another eBGP neighbor.
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Author Closing Comment

by:meade470
ID: 39276486
Thanks for the insight!
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