Clarification about where to apply PBR

[stephenshaw]

Hi,

I read the following from the Cisco config guide for the Catalyst 4500;

"You specify PBR on the incoming interface (the interface on which packets are received), not outgoing interface. "

I'm confused by the interpretation of what is considered the "incoming interface."

I have a 4500 switch that has a port-channel WAN connection to a fiber ring. My understanding is that I apply PBR to the port-channel. But the statement above indicates that possibly I apply PBR to the LAN interface??

access-list 101 remark Video Conferencing Devices

access-list 101 permit ip 10.x.y.5 0.0.0.0 any

!

route-map video-qos-out permit 10

match ip address 101

set ip next-hop 10.a.b.7

exit

!

Interface Po1

ip policy route-map video-qos-out

Appreciate anyone's comments on this.

Thanks,

Steve

[Reza Sharifi · Accepted solution]

Hi Steve,

The policy is applied to the incoming interface (LAN), but the route-map match is applied to the outgoing interface

Have a look at this doc with an example (WAN router config)

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009481d.shtml

HTH

[Amit Singh · Accepted solution]

Hi Steve,

Adding to Reza's post. You apply the policy map on the interface which is closeset to the source. PBR is basically a conditional source routing and depending upon the interested source traffic, you route it to  a different interface. It should be applied to the closet LAN interface. for exampl if you have a router with 2x WAN interface W1 and W2 and a LAN interface L1. If you wanto direct all the traffic from subnet X from the LAN to have a W1 as primary and W2 as back up, you apply the policy map on the L1 interface to direct the traffic accordingly.

HTH,

-amit singh

[stephenshaw]

Hi,

I understand what you are referring to when using two separate physical WAN interfaces but what I have is 1 WAN interface with equal paths to two different locations, A and B. I can't route it to a different interface, I need to route it to a different destination.

So just to clarify, the 4500 switch hosts both the LAN and WAN connections, I apply the PBR to the LAN interface and set the "ip next-hop" to the WAN IP address of location A (Location A being where I want this specific traffic to go) and normal routing remains as is. Am I correct in this??

The LAN interface I would need to apply the PBR would actually be a dedicated "interface VLAN xx" that is used only for our video conferencing.

Thanks,

Steve

[Thotsaphon Lueangwattanaphong · Accepted solution]

Hi,

    You need to apply it for inbound traffic coming in the particular interface. In your case it's the inteface that is used as gateway of video conferencing traffic.  What type of your wan link are you using? Point-to-Multipoint?  If siteA and siteB are diferrent, I think you can just define static routes pointing to each location.

HTH,

Toshi

[stephenshaw]

Hi Toshi,

Site A and B are on a fiber optic ring and route using OSPF. The site C (where PBR needs to be applied) is also on this ring, also using OSPF. It's simply using two GigEthernet ports configured in a port-channel to connect to the ring.

With the feedback from you, Amit and Reza, I now have a crystal clear understanding of how I need to change my original config.

thanks,

Steve