[VLAN] pktgen and sniffing VLAN packets

[Ben Greear]

Ian Brown wrote:
> Ben,
> Thanks.
> When I remove the "vlan_id" command from the script I do see PKTGEN
> packets on UDP port 9.
>
> These are captured by "tcpdump -f udp port 9"
>
>
> (UDP port 9 is used by default by PKTGEN, I assume that most people
> here probably know ).
>
> The thing is that I do want to generate VLAN tagged traffic.
>
> BTW, if I do configure a VLAN on eth0 , I do see VLAN packets (pavkets
> with ethertype of VLAN),  when sniffing with something like
> "tethereal -R "vlan and host x.y.z.q
>
> Any idea why with pktgen I cannot see VLAN traffic ?
>   
It's not pktgen:  hw-accel NICs strip the vlan tag on ingress, so you really
are generating vlan packets, it's just that the sniffer can't see the tags.

Sniff the VLAN device:  Anything on it had the VLAN tag on the wire.

Ben

-- 
Ben Greear <greearb at candelatech.com> 
Candela Technologies Inc  http://www.candelatech.com