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Sniffing QoS packets on HP procurve 2650

Occasional Visitor

Sniffing QoS packets on HP procurve 2650


We have a device plugged in in port 1 on a 2650. The device has no QoS enabled but we have set qos priority 7 on port 1 (interface 1 qos priority 7).

I have also plugged in a Linux-box on port 8 in the same switch and put port 8 as monitor port monitoring port 1, because i wan't to sniff the packets with tcpdump.

As far as i get it if QoS priority is set to 7 the ToS field in the packet should at least have another value than 0x0? But all packets incomming or outgonig from port 1 seems to have the ToS field set to 0x0. I'm sniffing using command "tcpdump -nvi eth0".

Have i done something wrong?

I'm really no expert on networks.
Matt Hobbs
Honored Contributor

Re: Sniffing QoS packets on HP procurve 2650

What you're doing is setting the L2 802.1p priority. This is usually inserted into the VLAN tag, but on untagged ports it will add that priority bit when going through your tagged uplink ports.

To see soemthing in the L3 header, you need to insert a DSCP or ToS bit which is a different set of commands on this switch.
Occasional Visitor

Re: Sniffing QoS packets on HP procurve 2650

So, if i don't have tagged uplink ports, it's no meaning setting priority that way?

How about routers? If i have a router between two nets, is there anyway to set priority on traffic coming in on f.ex. port 1 on a switch 2650 on net A that keeps that priority through the router to a switch on net B?

What protocol (or whatever) do the router need to support, or is this not possible?