[c-nsp] MPLS VPN over mGRE - PMTUD?

[Benjamin Lovell]

If you are looking to do this for setting the MPLS MTU dynamically then I don't think this will help as starting with our forwarding infrastructure rewrite in 12.4(20)T (I would need to check to be sure when/if in other code trains) we lost the ability to set the MPLS MTU on tunnel interfaces. 

See CSCth11646.


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          .            .          Benjamin Lovell
          |            |          AS Video Practice
         |||          |||         Cisco Customer Advocacy
       .|||||.      .|||||.       Research Triangle Park, NC
    .:|||||||||:..:|||||||||:.    Email:  belovell at cisco.com
             cisco            desk:919.392.8255 cell:203.509.1562
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On Sep 29, 2010, at 3:17 PM, Alasdair McWilliam wrote:

> Hi List,
> 
> Apologies if this is hidden in the list somewhere, but I've done a bit of Googling and can't find too much.. so here goes!
> 
> I'm looking at implementing an MPLS VPN over mGRE solution to facilitate routing instance segregation across multiple, geographically separate sites, across a third party Layer 3 infrastructure. (12.2SRE for 7200, IOS-XE 3 for ASR1k and looks to be coming into ISR G2 in 15.1T.) However given the mix of GRE encapsulation to provide the PE-PE connectivity, I'm a bit worried that apps might have a hissy fit.
> 
> My question is, does anyone know if it's possible to enable PMTUD with this feature? I've got it setup in a lab and the Tunnel0 and Tunnel1 interfaces cannot be directly modified from the CLI (they don't appear in config either...)
> 
> The next best thing I can see would be Dynamic L3 VPNs over mGRE, but that isn't available on the platforms I use, and I really don't want to go as far as to enable full blown MPLS over point to point GRE tunnels if I can at all avoid it!
> 
> Any tips? :-)
> 
> Cheers
> Al
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