Route-map upper limit

Hi all

I am looking to deploy some route maps on a BGP config in a prod environment, it is quite critical, and whilst not overly latency senitive, I want to take care not to bog the kit down. I am using new Nexus 7K's kit so quite powerful.

I have 2 questions....

1. Is there a number of statements that you should try to not go beyond when using route maps in BGP? The aim of the route maps will be along the lines of "if you match this prefix, set the next hop to be this". THis could happen for each service we are configuring which could be anywhere up to around 30 I guess.

2. There are other route maps to just allow prefixes into BGP, I want them to reference the prefix lists from point 1. Rather than doing multiple entries I was going to do 1 permit statement with a "match this, or, match this, or, match this" etc.... Is a match statement one line after the other an OR or an AND?

Many thanks

Comments

  • peetypeety ✭✭✭

    On a consulting client (ISP) that I support on the side, their outbound route maps are probably on the order of 85-100 clauses on Cat 6504/Sup720-3BXLs, and although the CPU is slow, they do just fine and I don't think convergence is any slower than if they didn't have those route maps. Inbound side is probably only 20-30 clauses, and that's still fine for 500k routes inbound.

  • Thanks for the reply and info. Looking to deploy a similar amount I guess so should be fine.

    Found out that point 2 is a logical OR in all route maps when matching the same type... e.g. 3 x prefix lists will be an OR. Can apparently AND if the types are different, so match a prefix list AND an ACL.

    https://supportforums.cisco.com/discussion/11542461/route-map-and-or-logical-algorithm

  • peetypeety ✭✭✭

    Also, remember that on some platforms, BGP route maps can utilize the 'continue' operator. This allows you to match certain parameters and set certain parameters, then instead of exiting the route map in a "first match and done" basis, you jump forward (must be forward, cannot ba backward) to a particular clause. The set actions you've done are preserved (though I don't know if subsequent matches reference the original data or the altered data) and you can do more matching and setting. I find it somewhat tricky but incredibly useful.

  • Many thanks for the replies all. 

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