Date: Thu, 03 Aug 2000 22:15:21 -0500 From: Bob Van Valzah <Bob@WhiteBarn.Com> To: freebsd-net@FreeBSD.ORG Subject: VLAN MTU? 1500? 1504? Why? Message-ID: <398A3549.902A31F5@WhiteBarn.Com>
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I'm about to try setting up VLANs on FreeBSD. I haven't yet found any
mention of VLANs in the FreeBSD documentation. The web pages I've read
on the subject seem to indicate that there's some dissension in deciding
how hosts with VLAN interfaces should handle the extra 4 bytes required
for the VLAN header.
One camp seems to be saying that the NIC's idea of MTU for the physical
interface should be raised to 1504 to allow room for this header so that
the VLAN interfaces can maintain the usual 1500-byte MTU.
Another camp seems to feel that the 1500-byte MTU of the physical
interface is sacred and suggests that the VLAN interfaces should have an
MTU of 1496.
What're the pros and cons of each approach? Is there a consensus as to
which would be a better default?
Thanks,
Bob
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