VLAN on SheevaPlug

[JonasR]

Hi,

some one got VLAN on his sheevaPlug running? I try it since some days but cant get it run.

My /etc/network/interfaces:

Code:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto eth0 vlan4 lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

# VLAN 4
iface vlan4 inet static
address 192.168.0.10
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255
mtu 1500
vlan_raw_device eth0

So the adapter is configured right:

Code:

debian:/etc/network# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:43:xx:xx:xx
          inet addr:x  Bcast:x Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:66251 errors:0 dropped:0 overruns:0 frame:0
          TX packets:237 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4818325 (4.5 MiB)  TX bytes:21222 (20.7 KiB)
          Interrupt:11

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:74 errors:0 dropped:0 overruns:0 frame:0
          TX packets:74 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:7952 (7.7 KiB)  TX bytes:7952 (7.7 KiB)

vlan4     Link encap:Ethernet  HWaddr 00:50:43:xx:xx:xx
          inet addr:192.168.0.10  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:692 (692.0 B)

But I dont get any VLAN tag if I trace with WireShark :/ Some one can help?

[JonasR]

No one got any idea?

[tylernt]

I know not all NICs are able to support VLANs, and for some NICs that do, the driver doesn't support it. You may be able to reduce the MTU to 1496 to allow for the extra 4 bytes of the VLAN tag to fit within the standard 1500-byte packet, but there's no guarantee it will work. Even if it does, I suspect that will only help for outgoing packets and you'll prolly have to change the other routers, switches, and hosts on your network to 1496 as well, in order to receive.

If MTU 1496 doesn't help, you may be able to contact the maintainer of the kernel driver for the Sheeva's NIC and ask them if the hardware or driver does or could support tagged VLANs.

[JonasR]

Thanks =) Finally i got a clue why it wont work.

[sfzhi]

I know not all NICs are able to support VLANs, and for some NICs that do, the driver doesn't support it.

Could you please elaborate? What kind of support is required from the NIC?

I was under the impression that VLAN was just another protocol running on top of Ethernet. So it's basically "Ethernet over Ethernet", similar to ESP in transport mode, only one level lower on the protocol stack (and without encryption, of course). In that case all the NIC (and the driver) has to do is pass the frames to/from the software, which it does anyway. Am I wrong about this?

[tylernt]

In theory yes a tagged VLAN packet is just another datagram. Unfortunately, some drivers, NICs, and even switches make certain assumptions about what an Ethernet frame should look like, either because someone was lazy / ignorant / cheap or just trying to improve performance with TCP offloading etc. Typically this has to do with MTU issues (not liking 1504-length packets) but what trips some things up is the fact that the VLAN tag is inserted into the middle of the frame -- drivers or devices looking for certain bytes in certain places fail, because some bytes get shifted over by 4 bytes.

With good quality network gear and code, VLANs typically work just fine though.

[JonasR]

Sorry for the late answer 

The trick with decrasing the MTU doesnt work for me. Ive informed the distributor... Lets see what comes out