[c-nsp] C65K: Any significant correlation between import filter route-map complexity and BGP Router process utilization?

[Nick Hilliard]

On 03/09/2010 20:36, Mack McBride wrote:
> Prefix lists are heavily optimized while as-path handling is not,
> especially if you use regexes.
> Standard community lists are easier to process than extended community
> lists.

This is because regexps are computationally rather heavyweight, whereas
integer comparison is rather fast.  This isn't anything to do with
optimisation; it's simply a matter of the inherent complexity of what
you're trying to do.

So, where you use a regexp in a complicated configuration, or a
configuration which needs to get evaluated lots of times, this is going to
chew RP CPU, no matter how simple

Expanded community lists and as-list lists both use regexps, so if you use
them, they are going to end up using lots of CPU.  On standard community
lists, you just specify the community number which is evaluated using an
integer comparison, so it's much faster.

Nick