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QoS on a Cisco IRB Network. What can be done?

Hello,

Is there any kind of QoS we can implement with an IRB setup?

I have included network configs. There are three sites which need to be bridged due to some non-routable software. Although, the customer also wants ip handsets. The IP phones are connected to the routed interfaces at each site with the intention of applying QoS. But the QoS just doesnt work... The service policy applied to the interface doesnt see any prioritised traffic. The IP phones are definitely marked as DSCP 46..

The Routers are all Cisco 1721's with IOS 12.4.

As you can see from the configs I have tried LLQ. But it just doesn't seem to work... I guess because it's a L2 interface im trying to apply the llq policy onto? Will any other type of QoS work?

The sites are linked by 2meg LL's via the S0 interfaces.

Any help on this matter would be greatly appreciated.

Thanks in advance

Matt

6 REPLIES
VIP Purple

Re: QoS on a Cisco IRB Network. What can be done?

Hello,

the service policy would need to be assigned to a Layer 3 interface in any case, for it to work. Since you are using IRB with BVI interfaces, you might want to try and apply the service policy to the BVI interfaces. In addition, you could also try and match on TCP port 1720 and UDP port range 16384 thru 32767, which are typically used by Cisco IP phones. So your access list would look like this:

access-list 100 permit tcp any any eq 1720

access-list 100 permit udp any any range 16384 32767

HTH,

GP

Re: QoS on a Cisco IRB Network. What can be done?

Hi GP,

Thanks very much for your comments :).

But i have already tried it unfortunatly :(. llq is not not supported on BVI interfaces. Also, I'm sure the voice traffic is being tagged correctly.

If I apply the policy to e0(Voice interface) and I do a sho policy-map interface ethernet0. I can see priority packets in the policy.

Kind Regards

Matt

Re: QoS on a Cisco IRB Network. What can be done?

Just a thought?... Is it possible to bridge traffic over a GRE tunnel? And could that be used in our scenario perhaps??

Thanks

Matt

Re: QoS on a Cisco IRB Network. What can be done?

Hi,

you could bridge across a lot of things including GRE. The main question remains: how to differentiate the traffic on the outgoing interface based on what is behind all encapsulation headers.

QoS pre-classify works for GRE tunnels, and could be worth a try.

The second thing coming up to my mind are qos-groups. Can you try to sort incoming packets into different qos groups and use the qos groups for your output policy?

Hope this helps

Martin

Re: QoS on a Cisco IRB Network. What can be done?

Thanks for that, I think the QoS pre-classify GRE tunnel method should work fine :). But does anyone have some config examples of bridging over GRE?? I have only ever routed over GRE tunnels...

I have used qos pre-classify before.

Would just like to get it clear in my head.

Many thanks in advance

Matt

Re: QoS on a Cisco IRB Network. What can be done?

Just to let you all know.. Bridging over GRE tunnels doesnt seem to work.. Tried everything!! The commands required are not available.

We have gone down the route of subnetting/routing the customers whole network.

Thanks for all the help though.

Matt

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