03-26-2009 02:04 PM - edited 03-04-2019 04:07 AM
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?
03-26-2009 02:30 PM
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
03-26-2009 03:21 PM
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
03-27-2009 12:49 AM
Hello James,
a good document for enteprise multihoming with NAT and BGP is:
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a0080091c8a.shtml#wp30809
Actually, there is a good example in the Jeff Doyle's book where route-maps are used with NAT.
Hope to help
Giuseppe
03-27-2009 08:07 AM
Thanks, Guiseppe!
I will take a look at link and Doyle.
Paresh.
03-27-2009 08:06 AM
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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