[j-nsp] MPLS MTU Juniper vs. CISCO

Wed Jun 6 02:25:24 EDT 2007

Hello!

Now we have cisco core network with MPLS MTU = 1526, for transit EoMPLS.

1518 - Ethernet + vlan .1q tag

8 - 2 MPLS Label

1518+8 = 1526

Example:

interface GigabitEthernet0/1.15

 description PE1

 encapsulation dot1Q 15

 ip address 1.1.1.30 255.255.255.252

 tag-switching mtu 1526

 tag-switching ip

!         

On Juniper box, MPLS mtu  automatically recalculated from MTU physical
interface.

And now, to set up mpls mtu 1526 on Juniper box we have  configuration:

>show configuration interfaces ge-0/1/4 

description "link to cisco CORE";

vlan-tagging;

mtu 1556;

unit 15 {

    description MSN-MFIST1-PE3;

    vlan-id 12;     

    family inet {

        mtu 1500;

        address 1.1.1.29/30;

    }

    family mpls {

        mtu 1526;

    }

}

What correct physical MTU, MPLS MTU must setup on Juniper box for the
organization of a joint CISCO and JUNIPER MPLS network.

Igor.