Catalyst 6509 stripping dscp header information

[danielseehof]

Hi,

does anyone know why my catalyst 6509 is stripping the dscp information out of the ip header. Setup is as follows: Alcatel IP phones connected to on of eight 4507s floor switches which are connected to a pair of 6509s running ospf on the uplinks.

My IP phones setting the dscp value to 0x28 or 40 (decimal). If I have a phone call to another IP phone on the same 4507 the dscp value is kept and reaching the receiving phone. As soon as a call is routed over the 6509s the value is stripped and, my guess, the packet not entering the priority queue on the switch.

Any ideas why and how to change this??

Thanks,

Daniel

[Gilles Dufour]

I'm not an expert in this but looks like you may need 'mls qos trust dscp'

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/121_5cex/cmdref/m1.htm#74769

Regards,

Gilles.

[danielseehof]

Hi,

even though the header information is now retained it seems to me as the 6509 is treating the packets as if they weren't tagged at all. Does anyone know of a possibility to find out whether packets are piped through the srict priority queue or not. I have the feeling that in our case the aren't, because I do get strange effects where packets arrive at their destination in bursts of 10-20 in the very same millisecond whereas this never happens if I skip the 6509s.

Any ideas?

Thanks,

DS