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New Member

new BGP feature. Load sharing over unequal cost links

Hi All,

BGP now has a feature to allow some load balancing between unequal eBGP peers.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t2/ftbgplb.htm

I am going to try this out either this week or next and am looking around to see if anyone else implemented it.

If so, would you mind sharing how the change went for you and what gotchas to look out for?

thanks very much

amanda

  • WAN Routing and Switching
4 REPLIES
Cisco Employee

Re: new BGP feature. Load sharing over unequal cost links

The only thing I would point out is that this feature follows the "bandwidth" configure on the interfaces to determine what traffic share will be assign to each neighbor. Nevertheless, you have to remember that the load-sharing will be based on the 16 CEF buckets and might not be exactly in the same proportion you expect.

Hope this helps,

New Member

Re: new BGP feature. Load sharing over unequal cost links

So far, so good. I managed to get the load balancing up and running on a trial basis using 3 routes.

I have decided to try and also add the default-route into the list of routes that load-share; but for some reason, the default route is not making it into multipath... let alone load sharing.

Do i need to remove the unequal cost load-sharing configuration and make it work in multipath before trying to re-enable the unequal cost load sharing?

Cisco Employee

Re: new BGP feature. Load sharing over unequal cost links

You should be able to get the unequal load-share functionality to work as well as with any other routes. Make sure you reset the BGP session after you configure the dmz-link feature.

I just did a quick test and here's the output:

R1#sh runn | beg bgp

router bgp 1

no synchronization

bgp log-neighbor-changes

bgp dmzlink-bw

neighbor 192.168.12.2 remote-as 2

neighbor 192.168.12.2 dmzlink-bw

neighbor 192.168.16.6 remote-as 2

neighbor 192.168.16.6 dmzlink-bw

maximum-paths 2

no auto-summary

!

R1#sh ip bgp 0.0.0.0

BGP routing table entry for 0.0.0.0/0, version 2

Paths: (2 available, best #1)

Multipath: eBGP

Advertised to update-groups:

1

2

192.168.12.2 from 192.168.12.2 (2.2.2.2)

Origin IGP, localpref 100, valid, external, multipath, best

DMZ-Link Bw 25 kbytes

2

192.168.16.6 from 192.168.16.6 (6.6.6.6)

Origin IGP, localpref 100, valid, external, multipath

DMZ-Link Bw 50 kbytes

R1#sh ip cef 0.0.0.0 0.0.0.0

0.0.0.0/0, version 23, epoch 0, per-destination sharing

0 packets, 0 bytes

via 192.168.12.2, 0 dependencies, recursive

traffic share 2

next hop 192.168.12.2, Serial2/0 via 192.168.12.0/30 (Default)

valid adjacency

via 192.168.16.6, 0 dependencies, recursive

traffic share 5

next hop 192.168.16.6, Serial3/0 via 192.168.16.0/24 (Default)

valid adjacency

0 packets, 0 bytes switched through the prefix

tmstats: external 0 packets, 0 bytes

internal 0 packets, 0 bytes

Hope this helps,

New Member

Re: new BGP feature. Load sharing over unequal cost links

thanks mate, but I am sure you are right; but i had to backout of this project yesterday afternoon. My router crashed with a software error and i believe it may have had something to do with this configuration because this is the only thing I had changed on the router and it has not done a crash before.

I am afraid i am going to have to go back to the tried and true divide and conquor method and force some traffic down one path and some down the second.

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