On Tue, Aug 28, 2001 at 12:54:18PM -0400, Garrett Wollman wrote:
> <<On Tue, 28 Aug 2001 01:05:32 -0400, Mike Tancsa <[EMAIL PROTECTED]> said:
>
> > Can anyone tell me why the VLAN code might be causing my switches (ciscos)
> > to see a lot of runt frames when the interface is in 802.1q trunking mode ?
>
> It's possible that the Cisco is (bogusly, IMHO) trying to enforce the
> Ethernet minimum frame length on the *de*capsulated frames. If you
> send a frame that's less than 60 octets long, it gets encapsulated
> (adding another four octets) and then padded by the interface up to 64
> octets. After the encapsulation is removed by the receiver, the frame
> appears to only be 60 octets long.
>
> I'd call it a Cisco bug. The minimum frame length in Ethernet arises
> from the electrical parameters of the original CSMA/CD Ethernet
> design; what matters is the number of clocks the transmitter is
> active, not the length of the payload.
But doesn't the switch have to assume that the VLAN will be attached to
some non-trunked ports, in which case the packets must be an appropriate
length. From a switch vendor's perspective the case of a VLAN with no
non-trunked ports is going to be a bizzare edge case.
-- Brooks
--
Any statement of the form "X is the one, true Y" is FALSE.
PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4
PGP signature
