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New Member



I am runing muticast in my network. now i would like to implement QOSas i am seeing lot of drops while pining to multicast server. For the same i planning to give high priority to multicast and any queing tech.

pls give me the solution


sateesh kumar.k

Hall of Fame Super Silver


Hello Sateesh,

in order to help you, may you provide a description of your network environment ?

What devices are using ?

Routers, multilayer switches.

Are you using a hierarchical design with two or three levels ?

Is it a campus network or you connect via WAN links to other sites ?

On a software based router you can use modular QoS and you can define a class of traffic by an extended ACL where as destination addresses you put your multicast groups and may be the source of the servers.

I did this recently and it works on C2811.

When it comes to switches it is a different matter, QoS for multicast is provided by high end switches like 6500, 4500.

This because switches face the problem of multicast forwarding on the switch ports.

By the way, your ping test is to the multicast group address or the server source address ?

Hope to help


New Member



We core SW 6509 which is uplinks for my 3750 switches .

CORE SW -- SW 3750-1-- Balde servers(Runing multicast)

Core SW -- 3750-2 -- blade server ..

Multicast enabled on 3750-1 andrest other sw 3750-2 will join in the group.

We are useing for internal servers only. all the application are runing on multicast.


sateesh kumar.

Hall of Fame Super Silver


Hello Sateesh,

here is a reference to QoS config on 3750

"The switch supports some of the modular QoS CLI (MQC) commands. For more information about the MQC commands, see the "Modular Quality of Service Command-Line Interface Overview" at this site: "

Actually you need to configure an egress scheduler, a multiple egress queues manager using the 3750 SRR interface queues.

What you can do:

on the C3750 where the source is connected you need to mark the traffic with DSCP and 802.1 COS settings.

OR have the source send marked traffic and trust (accept) it.

On all other switches you need to configure the SRR scheduler to the DSCP value of multicast traffic.

One queue can be a priority queue

However, I'm not sure that it will work it depends on implementation: multicast traffic could be queued on separate queue.

I've seen an example about an ACL for multicast traffic:

This example shows how to create an ACL that permits PIM traffic from any source to a destination group address of with a DSCP set to 32:

Switch(config)# access-list 102 permit pim any dscp 32

So it can work.

Hope to help


New Member



Thanks for your help. if possible pls provide the live config if you that i can study the same and i can maka a changes according to my network.

Thanks in advance..

bye sat.

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