I'm using a setup with a Linux box talking to a Netgear switch through an 802.1q trunk. The switch is used to 'fan out' the vlans on the trunk to ports on a network device. This is used to test various functionality on the device, and while testing packet filtering I ran into a problem. After some investigation I noticed the outgoing packets, generated by a custom program, were not being tagged correctly. Incoming traffic seems to be interpreted correctly, however. I first noticed it with layer 2 broadcast frames, but it seems to affect uni- and multicasts as well. Using tcpdump on the main interface and the vlan subinterface reveals that the outgoing broadcast is heard on both of them (while incoming replies are heard only on the subinterface), sans vlan tag. I also connected up a computer external to the setup via port mirroring, to verify what was actually going out on the wire. tcpdump on that box reported "vlan #0" on the outgoing frames, but correct vlan tags on the returning frames. The linux box with the trunk port reports this from uname -a: Linux auto3 2.6.10 #2 SMP Mon Jan 31 12:11:19 CET 2005 i686 GNU/Linux Has anyone got any idea what might be causing this problem? What can I do to remedy it? Thanks in advance. -- Niklas Karlsson niklas.karlsson@xxxxxxxxxxxxxxx Integration & Verification Engineer PacketFront Sweden AB http://www.packetfront.com/
