MPLS MTU and IP MTU on an interface

Unanswered Question
Dec 17th, 2007

I am working on a network running MPLS

MPLS MTU 1550 is set under gig interfaces while using show cef interface it shows that IP MTU is 1500

Will this cause some packet drops ?

Isn't it better to have same IP and MPLS MTU or not

thx

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gauravprakash Tue, 12/18/2007 - 04:45

MPLS mtu means how big a labeled packet can be. so MPLS mtu will be bigger than ip mtu. Each label it has over IP packet wil add 4 bytes.

So its ok to have it, just keep it uniform across the network.

regards,

Gaurav Prakash

mounir.mohamed Tue, 12/18/2007 - 04:55

It's depending on the MPLS application running on your network as each application (TE, VPN, Qos) add 4 bytes to the header for MPLS aplication labels.

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