BGP and static routes

Answered Question
Oct 29th, 2007
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Hi all. I have 2 routers running BGP(they are in the same AS) but each one has a different ISP connected on him.

I'm trying to force the traffic going to some specific networks that are now going over one link to go out the other link.

I was thinking of putting static routes to these networks on the router I want the traffic go out.

But I was wondering should I distribute these static routes through iBGP to the other router or should I put static routes on the other router that will point to the router I want the traffic to go out?

Thanks for any advice.

Correct Answer by saimbt about 9 years 9 months ago

Hi,


For outgoing traffic from your router u can use the Local Preference BGP attribute. It is the easiest to implement.


Use

Local preference for outgoing traffic

AS Prepend for incoming traffic


sample config:-


pri router


router bgp xyz


network abc


no synchronization


bgp log-neighbor-changes


neighbor remote-as


neighbor next-hop-self



neighbor




neighbor route-map 321 in


neighbor prefix-list 123 out




ip as-path access-list 1 permit ^pri-AS number$



route-map 321 permit 10


match as-path 1


set local-preference 200



Second router:-


router bgp


no synchronization


no bgp log-neighbor-changes


network


neighbor remote-as AS


neighbor route-map sec_link-Backup out


neighbor remote-as


neighbor fall-over


neighbor next-hop-self



no auto-summary



route-map sec_link-Backup permit 10


match ip address prefix-list yourcompany


set as-path prepend



ip prefix-list yourcompany seq 5 permit


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Jon Marshall Mon, 10/29/2007 - 05:16
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Hi Igor


if you are running IGBP between your 2 routers then you should look to use local preference within your AS which will prefer one exit point over another per route but will still fall back to the other exit point if a link goes down. See attached doc for explanation of local preference.


http://www.cisco.com/en/US/tech/tk1330/tsd_technology_support_technical_reference_chapter09186a00807597c7.html#wp1020583


if you are not running IBGP between your 2 routers you could use static routes but i don't think this is as clean or flexible.


HTH


Jon

Correct Answer
saimbt Mon, 10/29/2007 - 05:28
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Hi,


For outgoing traffic from your router u can use the Local Preference BGP attribute. It is the easiest to implement.


Use

Local preference for outgoing traffic

AS Prepend for incoming traffic


sample config:-


pri router


router bgp xyz


network abc


no synchronization


bgp log-neighbor-changes


neighbor remote-as


neighbor next-hop-self



neighbor




neighbor route-map 321 in


neighbor prefix-list 123 out




ip as-path access-list 1 permit ^pri-AS number$



route-map 321 permit 10


match as-path 1


set local-preference 200



Second router:-


router bgp


no synchronization


no bgp log-neighbor-changes


network


neighbor remote-as AS


neighbor route-map sec_link-Backup out


neighbor remote-as


neighbor fall-over


neighbor next-hop-self



no auto-summary



route-map sec_link-Backup permit 10


match ip address prefix-list yourcompany


set as-path prepend



ip prefix-list yourcompany seq 5 permit


IgorHamzic Tue, 11/13/2007 - 00:46
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Thanks for your great advice guys. Did something similar to your suggestions and works fine.

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