Question on about Policy Based Routing (PBR) on MSFC

Unanswered Question
Jun 12th, 2007

Hi everyone,

I have a question about Policy Based Routing (PBR) on MSFC.

Does MSFC1 process Policy Based Routing in software or in hardware ?

What about MSFC3 ?

The background of this question is as follows.

Our customer facing CPU utilization issue on MSFC1. The peak CPU utilization on the MSFC1 become about 30%. Hardware component of that Catalyst 6506 is as follows,

Catalyst 6506

SUP1A : CatOS 5.5(3)

MSFC1 : IOS 12.1(2)E

PFC1

The MSFC1 is configured with

8 VLAN interfaces

20 static routes (dynamic routing is not operating)

1 named ACL with 16 entries

2 numbered ACL with 50 entries each

I think above configuration does not effect CPU utilization so much. So I am doubting that PBR raises CPU utilization.

The following PBR configured on the MSFC1.

----------

route-map PBR permit 0

match ip address 111

set ip default next-hop xxx.xxx.xxx.xxx

route-map PBR permit 1

match ip address 222

set ip default next-hop yyy.yyy.yyy.yyy

----------

Now customer is thinking of upgrading the Cat6506 to Cat6504-E.

Hardware component of new Catalyst 6504-E is as follows.

Catalyst 6504-E

SUP720-3B : Cat IOS 12.2(17d)SXB11a

MSFC3

PFC3

And customer similarly uses same PBR configuration also on new Cat6504/MSFC3.

I understand I should test on both MSFC1 and MSFC3 to compare CPU utilization, however unfortunately I can not prepare those system now. So I posted it becasue I would like to know any information.

Would you please let me know MSFC1 process Policy Based Routing in software or in hardware ?, and what about MSFC3 ?

Your information would be appreciated.

Best regards,

I have this problem too.
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Jon Marshall Tue, 06/12/2007 - 23:54

Hi

I can answer at least part of your questionas i have just had to look this up myself.

PBR is supported in hardware on a 6500 by the Policy Feature Card and Distributed Forwarding Card. Certainly with a PFC3 PBR is supported in hardware with the following caveats (from Cisco doc)

=============================================

Policy-based routing (PBR) for route-map sequences that use the match ip address, set ip next-hop, and ip default next-hop PBR keywords.

=============================================

This is link to full doc for more details

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a00801609f4.html#wp1029188

AFAIK a PFC card will also support PBR in hardware with the same caveats but i could be wrong as i could find no definitive answer on the Cisco site.

Hope this has at least partially answered your question

Jon

ariela Wed, 06/13/2007 - 00:21

Yes, I agree with Jon,

your focus shall be the PFC, and not MSFC. The Policy Feature Card (PFC) and any Distributed Feature Cards (DFCs) provide hardware support for policy-based routing (PBR) for route-map sequences that use the match ip address, set ip next-hop, and ip default next-hop PBR keywords.

Check the release notes about specific behavior of PBR (for example: on 12.2 SX PBR traffic through switching module ports where PBR is configured is routed in software if the switching module resets -> CSCee92191)

For more informations:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a0080160a07.html#wp1027016

Another good advice is 'enable CEF' to improuve the PBR performances:

'ip cef'

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a008075fae6.html

Let me know

HTH

Andrea

mohammedmahmoud Wed, 06/13/2007 - 00:36

Hi,

I actually agree with both Jon and Andrea, but i just have one concern, AFAIK CEF is supported in HW starting from MSFC2 and not MSFC1.

HTH,

Mohammed Mahmoud.

snakayama Wed, 06/13/2007 - 01:13

Hi Jon, Andrea and Mohammed,

Thank you very much for your reply.

I understand I should focus on PFC not MSFC. According to the following URL,

http://www.cisco.com/en/US/products/hw/switches/ps708/products_white_paper09186a00800c9470.shtml#wp43942

----------

Policy-Based Routing TCAM and Adjacency Utilization

In Supervisor 2 with PFC2 and Supervisor 720 with PFC3, policy-based routing (PBR) is fully supported in hardware using a combination of the security and feature ACL TCAM and the hardware adjacency table.

----------

PBR is fully supported in hardware in Supervisor 2 with PFC2 and Supervisor 720 with PFC3. So in my case that using PFC1, I think PBR might not be fully supported in hardware.

Best regards,

ariela Wed, 06/13/2007 - 02:06

Correct, Shinichi,

I agree with Mohammed, you need at least a Sup2 MSFC2 PFC2.

HTH

Andrea

snakayama Wed, 06/13/2007 - 17:45

Hi Andrea,

Thank you very much for your reply.

I understand it and I plan to test whether PBR effect cpu utilization on SUP720-3B/PFC3/MSFC3.

Best regards,

Shinichi

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