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New Member

why can't the packet longer than 1460 byte through?because the isl trunk ?

I linked a 2924 switch to an 6506 switch through isl trunk,another 3500 switch is linked to the 2924 switch through isl trunk. It is strange that any packet longer than 1460 byte can't be pinged from the 3500 switch to the 6506 switch. But when I changed the link between 3500 and 2924 from trunk to aceess,every thing is ok now.Also when I ping from 2924 to 6506,everything is ok .Is this problem something to do with the isl trunk encapsulation?

3 REPLIES
Silver

Re: why can't the packet longer than 1460 byte through?because t

check your MTU size

Re: why can't the packet longer than 1460 byte through?because t

As above check your MTU.

The ISL frame encapsulation is 30 bytes, so if Ethernet packets are encapsulated, the range of ISL frame sizes are from 94 to 1548 bytes.

Check the output of the "show port x/x" command, "show mac x/x" command, and "show counters" for errors. Look for "MTU-Exced", giants/runts as they are possible indications of a ISL/dot1q config issue.

Hoep it helps.

Steve

New Member

Re: why can't the packet longer than 1460 byte through?because t

If the MTU size is being exceeded, what would be the best solution? Increasing the allowed MTU to something above 1500, like 1548 for every switch? Is there a different/better solution?

Thanks,

Matt

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