Outbound traffic engineering using BGP.

Unanswered Question
Mar 26th, 2009

We have dual-homed BGP, with AT&T and Sprint, with links from ISP terminating on different

chassis.

We also have different network blocks from each ISP, let's say block A, B, & C from ATT

and block X, Y, & Z from Sprint.

What we like to do, is if traffic is sourced from A/B/C, we always want to send it out to

ATT and if traffic is sourced from X/Y/Z, it is always sent to Sprint - as long as links

to ISP is up.

How can I do this using BGP?

I have this problem too.
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Giuseppe Larosa Thu, 03/26/2009 - 14:30

Hello Paresh,

BGP has a rich set of tools but all of them are confined in the "destination based" dynamic routing world.

For routing based on a source address the right tool is PBR with or without NAT.

(NAT can be done before/more inside for different reasons security performance ...)

Hope to help

Giuseppe

jpoplawski Thu, 03/26/2009 - 15:21

Hello,

This seems like a fairly general question, perhaps you can provide additional details. Are you looking to send AT+T networks over Sprint in the event of an AT+T outage. Do you have a public AS number? Is each block Provider Assigned or Provider Independent?

It definitely sounds like route-maps are the way to go, although I'm not sure I understand completely what you're trying to accomplish.

This is a basic overview from Cisco's site, http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a008009456d.shtml

however a different example is found in Routing TCP/IP Vol2 Page374.

Please provide additional info and review the documents to see if they are of any assistance.

JB

pkpatel Fri, 03/27/2009 - 08:07

Thanks, Guiseppe!

I will take a look at link and Doyle.

Paresh.

pkpatel Fri, 03/27/2009 - 08:06

Hello JB,

Answer to all three questions above are "yes".

What I am trying to do is influence outbound traffic to take specific ISP link as long as it it available. I know this can be done using PBR. But, I am trying to do this within BGP.

I will look at TCP/IP Vol-2.

Thanks,

Paresh.

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