Service Policy to 2 interfaces on 3750 - How does it load balance?

[roger perkin]

I have a 3750 switch which has 2 Layer 3 interfaces connected to an ISP Managed Wan router.

I have 2 BGP peerings to the two physical interfacs on teh ISP router.

I have created a simple QOS policy which is going to police some traffic to 2Mb - I was then going to apply a service policy to the the outbound interfaces.

Question:

If I apply the service-policy to both interfaces Gi1/0/24 & Gi2/0/24 how will the QOS work, will I be in effect putting a 2MB policy onto each interface?

I am also curios as to how an interface is chosen as if I do a sh ip cef for a remote address it always chooses Gi1/0/24 as the outbound interface?

Thanks

Roger

[Jon Marshall]

Roger

Yes it will apply a 2Mb to each interface as they are separate L3 interfaces.

Edit - sorry, you did say there were two peerings.

BGP by default only selects one best path even if there are multiple equal cost paths. If you want it to use both paths then you can -

1) peer on loopbacks between your 3750 and the ISP router

or

2) assuing the peerings are EBGP add this to your config -

router bgp <AS>

maximum-paths 2

this should allow your 3750 to use both paths. Note that when using that command the AS PATH not only needs to be the same length but also consist of the same AS numbers ie. they must match exactly.  There is a command you can use to override this but you shouldn't need to as it is the same ISP so it should already be a match.

Note also this would only use both paths outbound to the ISP.  How the paths are used inbound depends on the ISP configuration.

Jon

[paul driver]

Hello

My understanding the 3750 doesnt support egress policing - you will need to apply the policng inbound lan facing

SRR is another option you can utilse

res

Paul