Michael,
Check:
http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst6500/ios/12
.2SX/configuration/guide/intrface.html#wp1041111
http://www.cisco.com/en/US/partner/docs/ios/interface/command/reference/
ir_l2.html#wp1030775
http://www.cisco.com/en/US/partner/docs/ios/fundamentals/command/referen
ce/cf_s3.html#wp1019645
I think it should be in there.
I couldn't get to any of these, even taking into account the wrapped
lines.
It is likely that you have configured an SVI or a VLAN on the 6509
for 9216 already.
If any VLAN that crosses the switchport is 9216, then you can't
adjust the MTU of the port to a value below 9216.
Do a 'show vlan' and also check all the SVI's for an MTU higher than
1504, then either reduce the MTU in those locations or I think you
could also restrict the large VLAN from being sent on the trunk
Once you define the L2 MTU, packets on that VLAN can traverse any
ports on that VLAN up to that MTU, but if you need to route them and
retain the L2 MTU then the L3 SVI must have the same MTU. You can
have the SVI different, say 1500, as long as you understand that the
packets will be fragged if larger than 1500, or dropped if the DF
bit is set. If you have defined an SVI to a 9k+ MTU, that will
force the L2 interfaces on that vlan to be the same since they must
carry that size packets.
I finally sorted this out: If I was setting the MTU on a routed
interface, then I could set the MTU to anything up to 9216B (using the
mtu interface command), however, if I was trying to set the MTU an a
switchported interface, then the mtu command would only allow me to
change the MTU to the value defined in the global "system jumbmtu"
command - this is a feature not a bug.
Thanks,
Michael
--
Michael Robson | Tel: +44 (0) 161 275 6113
Networks | Fax: +44 (0) 161 275 6120
Net North West | Email: michael.rob...@manchester.ac.uk
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