[c-nsp] Question on the Use of Policy Based Routing

[Andrew Miehs]

On 07/03/2012, at 3:56 PM, Oliver Garraux wrote:

> On Tue, Mar 6, 2012 at 11:47 PM, Andrew Miehs <andrew at 2sheds.de> wrote:
>> Does PBR still cause the performance issues it did in the past, forcing every packet through the CPU?
>> 
>> Andrew
> 
> I think it varies by platform. IIRC, PBR can usually be done in
> hardware, except if denies are used in the ACL's.

Just found my own answer!

http://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html

"IP PBR can now be fast-switched. Prior to Cisco IOS Release 12.0, PBR could only be process-switched, which meant that on most platforms the switching rate was approximately 1000 to 10,000 packets per second. This speed was not fast enough for many applications. Users who need PBR to occur at faster speeds can now implement PBR without slowing down the router."

and

"Beginning in Cisco IOS Release 12.0, PBR is supported in the Cisco Express Forwarding (CEF) switching path. CEF-switched PBR has better performance than fast-switched PBR and, therefore, is the optimal way to perform PBR on a router."

- I would still try and look for normal routing alternatives though as you could very quickly set up a routing loop in larger installations.

Regards

Andrew