mVPN configuration for 1500 byte packets with DF set

[leedavies]

Hi

I have a L3 VPN customer that has a requirement to multicast 1500 byte packets unfragmented across our MPLS network. I have configured:

• PIM-SSM in the core
  
• MTU of all MPLS enabled links is 1536
  
• IP MTU of all MPLS enabled links is 1500
  
• MTU of PE-CE links is 1500
  
• MDT SAFI on all PE's and RR's
  
• Default MDT
  
• Data MDT
  

The mVPN works OK for packets up to 1472 bytes with DF set.

I suspect that removing IP MTU 1500 from all PE-P and P-P links may help. I have been unable to find any documentation on how to increase the MTI's MTU to avoid fragmentation. Can any of you suggest how to get this working or point me to design documentation please?

The PE's in question are 7600-RSP720 - 12.2(33)SRD4 and ME6524 - 12.2(33)SXH7.

Thanks in advance

Regards

Lee

[Luc De Ghein]

Hi Lee,

You can try the following:

"mdt MTU <>" hidden command under ip vrf <>

Thanks,

Luc

[leedavies]

Hi Luc

The mdt mtu command didn't fix the issue for us.

We fixed it by removing "ip mtu 1500" from the PE-P links.  This allowed the MTU of the MTI to be large enough to accomodate the 1500 byte C-packet and GRE header without fragmentation.

Thanks for your help

Lee