VLANs, Cisco Catalyst 5500 (CatOS) and a Realtek 8100 series

Hi all,

This is my first project using the vlan support in linux, but I hope
to use it extensively in the future (as my company is *finally* moving
to a pure cisco network next quarter, woo!).

Here's my setup:

Firewall running 2.6.11.4 kernel, with VLAN patch v1.8 (the one that
comes with this kernel ver, also the latest I believe).
The NIC connected to the switch is a Realtek 8100 series that I
believe should support the extra MTU size (8139too driver)
-- Kernel output for the ethernet card, if you want it.
Mar 19 22:58:40 istanbul kernel: eth3: RealTek RTL8139 at 0xe800,
00:e0:3c:7e:55:55, IRQ 11
Mar 19 22:58:40 istanbul kernel: eth3:  Identified 8139 chip type 'RTL-8100'
-- End

Cisco Catalyst 5500 Running CatOS 
-- "show version" gives a festive
WS-C5500 Software, Version McpSW: 5.5(18) NmpSW: 5.5(18)
Copyright (c) 1995-2002 by Cisco Systems
NMP S/W compiled on Dec 16 2002, 15:34:48
MCP S/W compiled on Dec 16 2002, 15:30:03

System Bootstrap Version: 3.1.2

Hardware Version: 1.3  Model: WS-C5500  Serial #: 069026231

Mod Port Model      Serial #  Versions
--- ---- ---------- --------- ----------------------------------------
1   0    WS-X5530   007604769 Hw : 1.5
                              Fw : 3.1.2
                              Fw1: 3.1(2)
                              Sw : 5.5(18)
         WS-F5520   007574879 Hw : 1.0
2   0    WS-X5530   007621510 Hw : 1.5
                              Fw : 3.1.2
                              Fw1: 3.1(2)
                              Sw : 5.5(18)
         WS-F5520   007483963 Hw : 1.0
3   24   WS-X5225R  024916723 Hw : 3.4
                              Fw : 4.3(1)
                              Sw : 5.5(18)
4   24   WS-X5225R  015415233 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
5   24   WS-X5225R  014909080 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
6   24   WS-X5225R  013429065 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
7   24   WS-X5225R  013429102 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
8   24   WS-X5225R  022503596 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
9   24   WS-X5225R  022504597 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
10  24   WS-X5225R  021639581 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
11  24   WS-X5225R  015477505 Hw : 3.3
                              Fw : 4.3(1)
                              Sw : 5.5(18)
12  24   WS-X5225R  012787567 Hw : 3.1
                              Fw : 4.3(1)
                              Sw : 5.5(18)
--

Its odd, I set up the vlans I want on the switch, set up the trunking
on the port that the firewall is connected to, and vconfig the vlans
to the interface on the firewall, but once I bring the vlan'd
interface up, it will transmit packets, but not actually receive
anything except for what tcpdump identifies as "Unknown IPX packets".
hooray. Anyone have any ideas? I'll be glad to supply more information
if need be. I suspect an MTU issue, but I'm not too sure.

Thanks in advance.