I have a box with a via_rhine adapter connected to a cisco 2950. The light doesn't flash, but the 'runt frame' count is almost the same as the good packet count. With vlan enabled, I'm not sure that the via_rhine adapter does any padding at all, so I get some pretty tiny frames. Doesn't seem to affect functionality in any way though. James > -----Original Message----- > From: vlan-bounces@xxxxxxxxxxxxxxx [mailto:vlan-bounces@xxxxxxxxxxxxxxx] > On Behalf Of Sascha Pollok > Sent: Thursday, 31 August 2006 17:30 > To: Linux 802.1Q VLAN > Subject: Re: [VLAN] 802.1Q ARP frame size? > > > >>> I noticed that the 802.1Q ARP frame size generated by the Linux > > > driver > > >>> (V1.8) is only 64 octets (not 68 octets). > > >>> > > >>> It seems the minimum frame size for 802.1Q is 68 octets. > > >> The 64-octets is an ethernet physical level issue, not a VLAN issue, > > > so > > >> there is no need to pad the frame to 68 bytes. > > >> > > > > > > So what happens when a switch untags the vlan tag and sends the > untagged > > > packet out a port? Is it the responsibility of the switch to then pad > > > the packet? Or does this just happen automatically anyway? > > > > It's the switches duty..and most NIC's hardware will do the padding..I > > assume switch hardware can easily do the same. > > When I first was sent a Cisco 2970-24TS switch when it was brand new, > I noticed lots of "too small but good" frames and orange blinking of the > port's LED when receiving minimum-sized dot1q frames. It turned out that > these switches require 68 byte tagged frames minimum. If they receive > 64 Byte frames, they still forward it but complain about it. This is > unfortunately not fixable in the IOS because the bug is in the burned-in > software on the ASICs. There is a patch around for the e1000 that > pads the packets to 68 bytes instead of 64. I guess newer ASICs do not > have this bug. > > Just my $0.02 > Sascha > > _______________________________________________ > Vlan mailing list > Vlan@xxxxxxxxxxxxxxx > http://www.candelatech.com/mailman/listinfo/vlan
