On Wed, Nov 28, 2001 at 08:17:53PM -0000, David Laight wrote:
> AARRG I got the number wrong - 1514 bytes between destaddr and end of data.
> I've clearly not written enough ethernet drivers recently :-)
> 
> Not read 802.1Q - but you can't (surely) use a protocol that adds
> 4 bytes to the maximum length of an ethrnet frame.

Really ?
tlp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        address: 00:00:c0:f1:ee:e9
	media: Ethernet autoselect (100baseTX full-duplex)
	status: active
	inet6 fe80::200:c0ff:fef1:eee9%tlp0 prefixlen 64 scopeid 0x1
vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        vlan: 574 parent: tlp0
        address: 00:00:c0:f1:ee:e9
        inet 132.227.63.133 netmask 0xffffff00 broadcast 132.227.63.255
        inet6 fe80::200:c0ff:fef1:eee9%vlan0 prefixlen 64 scopeid 0x8
vlan1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        vlan: 597 parent: tlp0
        address: 00:00:c0:f1:ee:e9
        inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255
        inet6 fe80::200:c0ff:fef1:eee9%vlan1 prefixlen 64 scopeid 0x9
vlan2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        vlan: 578 parent: tlp0
        address: 00:00:c0:f1:ee:e9
        inet 132.227.67.254 netmask 0xffffff00 broadcast 132.227.67.255
        inet6 fe80::200:c0ff:fef1:eee9%vlan2 prefixlen 64 scopeid 0xa

'man vlan' on a NetBSD system shows you:
     To be compatible with others 802.1Q devices, the vlan interface shall
     support a 1500 bytes MTU, which means that the parent interface will have
     to handle frames that are 4 bytes larger than the ethernet MTU. Drivers
     supporting this increased MTU are:
     -   drivers using the dp8390 core (ec(4), ne(4), we(4), possibly others)
     -   ea(4)
     -   eb(4)
     -   epic(4)
     -   ex(4)
     -   fxp(4)
     -   le(4)
     -   tlp(4)
     -   ti(4)
     -   xi(4)

I'm using it a work (talking with cisco or 3com 802.1q capable swicthes)
with ne, ex, le, tlp and ti ethernet interfaces.

--
Manuel Bouyer <bouyer@antioche.eu.org>
--