Solved: Public BGP peering weighted

gregwoodson · ‎03-21-2008

We have a public AS that we are advertising using two BGP peers. How can we change the weight or administrative distance on one to make it less preferable to incoming traffic?

Danilo Dy · ‎03-21-2008

The sample will work for both (1 x Router or 2 x Router in iBGP)

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Danilo Dy · ‎03-21-2008

Hi,

To enfluence incoming traffic, use PREPEND. You can also use MED but not all ISP honors MED.

If its not enough, try advertising your prefix in two in your preferred ISP and in one in your less-preferred ISP.

Regards,

Dandy

gregwoodson · ‎03-21-2008

Hey Dandy!

I appreciate the response. I cant seem to find good documentation anywhere regarding prepend or its use. This is what I dont understand at this point.

Thanks

Danilo Dy · ‎03-21-2008

Hi,

Check this link http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080093f2c.shtml

The link is HSRP and BGP, just focus on the prepend :) in your situation (R2 for example) you can PREPEND more....

set as-path prepend 100 100 100 100 nnn

...I think the maximum is 8 prepend

BTW, what is your setup? 2 x Router (each peer to different ISP) or 1 Router that peers to both ISP.

Regards,

Dandy

gregwoodson · ‎03-21-2008

Currently it is 1 router that peers to both ISPs. Within the next couple weeks- it will be 2 routers (then 3) peered to 3 different spots.

Danilo Dy · ‎03-21-2008

The sample will work for both (1 x Router or 2 x Router in iBGP)

gregwoodson · ‎03-21-2008

Thanks! I am implementing changes tonite. I will update on here if it fixed the issue.

Thanks again!

gregwoodson · ‎03-24-2008

This resolved the issue. Thanks!

yuhuiyao · ‎03-26-2008

for incoming traffic, you just have limited influence over the remote side's decision like AS prepend, or route origin (IGP/incomplete). MEDS will not work in multihomed scenario. If the remote side decides to use LP, it will override all your efforts.

The best way to control incoming traffic is to use different subnet mask to advertise the same route to different remote sides.