MTU on Interface

[olorunloba]

Deploying MPLS VPNs, and thinking of increasing the MTU on my interfaces because of fragmentation. Who knows the maximum MTU the follwing hardwares can take.

NM2E-2W, NM2FE2W, WIC-1T, WIC-2T on 3600

PA-4E1G, PA-2FE, on VIP4-50 and FE2IP on RSP4 on 7507.

A link would be appreciated aslo

[peter.fuchs]

Hi

As far as I know you need a MTU Size of about 1526

MTU + transport + ATOM + (MPLS Label)=

1500 + 18 + 0 + (4*2) = 1526

Link:

Jumbo/Giant Frame Support on Catalyst Switches

http://cisco.com/en/US/customer/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml#topic1

best regards

Peter

[olorunloba]

Yes, but I need to know if the router would be able to pass these "jumbo frames", both on the ethernet and serial. I'm conccerned about the hardware limitation.

[peter.fuchs]

Was not able to find anything specific about supported MTU sizes for the interfaces you need.

So the best thing would be to try it.

tag-switching mtu 1526

BTW: this MTU size you realy need only on your P routers.

[oettls]

You shouldn't have problems with the serials (WIC-1T, WIC-2T). Don't know the exact limit but you can e.g. increase the tag mtu to 1524. (6 Labels == 24 bytes is the maximum recent IOS versions support). If you deploy AToM you might need even more (control word, ...).

PA-2FE should support 1510 bytes (L2 payload), guess the same applies for FE2IP.

hth,

Stefan