Setting MTU on FE interfaces. Lack of documentation?

Unanswered Question
May 28th, 2009

I'm trying to find out

1. Which FE hardware supports >1500 byte MTU. (e.g. PA-FE-TX, PA-2FE-TX, HWIC-4ESW, HWIC-2FE, Fa0/0 on a 2811?)

2. What IOS version is necessary to effect this support (if IOS dependent at all).

3. What's the maximum MTU size which can be set with respect to (1) and (2) above.

What I've found so far is only a doc talking about Jumbo Frame support on Catalyst switches (not what I need).

Searching this NetPro forum seems to indicate that I'm not the only one looking for info along the lines stated above. I'm ok with searching and reading documention but the "feature" of whether a card has a "user settable MTU" doesn't appear to be mentioned in any docs at all. (Or am I mistaken?). Any Cisco guys reading this?

Option 2: We can go the "opensource" route. I ask everyone who might be interested to the answer to this to help compile the following matrix:

[Platform, Card, IOS ver, Max MTU]

Is there a less painful way to get the answers?


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Leo Laohoo Thu, 05/28/2009 - 20:16

Errr ... nearly every Cisco router, switches, etc support Jumbo Frames. Just what exactly are you trying to do?

Paolo Bevilacqua Thu, 05/28/2009 - 20:28

No, FE on cisco routers supports only standard MTU. If you need jumbo frames, get GE interfaces.

BENJAMIN TAN Thu, 05/28/2009 - 20:52

Quite a few FE ports DO support >1500 MTU even if not 9K MTU (which isn't what I'm asking).


[C1801, Fa0, any, 1600]

BENJAMIN TAN Thu, 05/28/2009 - 20:36

Not on the FE ports.

GE ports, sure.


[C720xVXR, PA-FE-TX, SRD1, 1530]

[C750x, PA-FE-TX in VIP4-50, 122.25S14, 1500]


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