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New Member

Tag-switching IP Issues


I have 2 routers with a FE link,

7206 ---Trunk---> switch 3560-48 ---> link WAN with FE to ---> 3640 --trunk->sw3560-48-->customers,

my Internet access is via the 7206 router.

I need to stablish a ibgp session to configure VPN-MPLS for some services, i set the mpls parameters and is posible to stablish the session,

ip cef is on, and i can see the TDP Neighbor UP between 7206 and 3640.

I have a switch 3560-48 connected to the router 3640, the link its a trunk, so i can use these ports for

internet customer access.

well, when I apply the tag-switching ip or mpls ip ont the interfaces between 7206 and 3640 link,

the customers that have only internet access via the 3640 router have problems to browse, and some other pages.

When I remove the tag-switching ip or mpls ip

the service normalizes.

could somebody help me with this issue

Thank you


Hall of Fame Super Blue

Re: Tag-switching IP Issues


This sounds like it could be an MTU issue. Could you try changing the MTU to 1520 on all MPLS enabled interfaces and retest.

You may also need to increase the MTU on your 3560 switches.


New Member

Re: Tag-switching IP Issues


Thank you for the information,

just to be shure,

I can use this command to modify the MTU on my switches?

sw(config)#system mtu 1520

so could you help me to define where i must to change the mtu because i am using trunks,

and which MTU must modify,

the mtu only or mpls mtu or both

i attach a diagram with the topology

Thank you for your help