Hello, What you're looking for is "allow-fragmentation"
http://www.juniper.net/techpubs/en_US/junos11.1/topics/usage-guidelines/ser vices-configuring-unicast-tunnels.html#configure-packet-reassembly (although this refers to ms-dpc, the mpc/trio behaves the same) I labbed this up to confirm: {master} jnpr@R1-RE0> show interfaces ae0.1 | match mtu Protocol inet, MTU: 1500 Protocol iso, MTU: 1497 Protocol multiservice, MTU: Unlimited {master} jnpr@R1-RE0> show interfaces gr-2/0/0 | match mtu Type: GRE, Link-level type: GRE, MTU: Unlimited, Speed: 10000mbps Protocol inet, MTU: 1476 Protocol iso, MTU: 1516 Flags: User-MTU {master} jnpr@R1-RE0> show configuration interfaces gr-2/0/0 unit 0 { tunnel { source 10.8.0.0; destination 10.8.0.1; allow-fragmentation; } family inet { address 1.1.1.1/30; } family iso { mtu 1516; } } {master} jnpr@R1-RE0> show isis adjacency Interface System L State Hold (secs) SNPA ae0.1 R2-RE0 2 Up 23 gr-2/0/0.0 R2-RE0 2 Up 21 Thank you, -- Doug Hanks - JNCIE-ENT #213, JNCIE-SP #875 Sr. Systems Engineer Juniper Networks On 3/12/12 4:49 PM, "EXT - li...@beatmixed.com" <li...@beatmixed.com> wrote: >Wanted to throw this out there to see if anyone else has solved this >problem before me. > >I'd like to set up an IS-IS adjacency over an Internet based GRE >tunnel. The tunnel comes up fine in my tests but the IS-IS adjacency >never forms. One can probably safely presume this is due to an MTU >issue -- the 1492 PDU size for IS-IS + 24 for GRE doesn't fit in the >1500 MTU this is all riding over. > >Juniper has a technical note which touches upon the issue: > >http://kb.juniper.net/InfoCenter/index?page=content&id=KB7848 > >... so I have some hope the problem is solvable... > >I'm using Trio linecards on MX platform. Technically speaking, I don't >want to enable fragmentation of my IP traffic. I'd like for path MTU >discovery to do its thing with that. Not quite sure I actually >understand (from the tech note) what I am supposed to do >configuration-wise to solve this... > >Here's a rough outline of my basic config (real simple): > >== R1 == > >set chassis fpc 2 pic 3 tunnel-services bandwidth 10g > >set interfaces gr-2/3/0 unit 0 tunnel destination x.x.x.3 >set interfaces gr-2/3/0 unit 0 tunnel source x.x.y.3 >set interfaces gr-2/3/0 unit 0 family inet >set interfaces gr-2/3/0 unit 0 family iso > >set protocols isis interface gr-2/3/0.0 point-to-point >set protocols isis interface gr-2/3/0.0 level 1 disable >set protocols isis interface gr-2/3/0.0 level 2 metric 1000 > >== R2 == > >set chassis fpc 2 pic 3 tunnel-services bandwidth 10g > >set interfaces gr-2/3/0 unit 0 tunnel source x.x.y.3 >set interfaces gr-2/3/0 unit 0 tunnel destination x.x.x.3 >set interfaces gr-2/3/0 unit 0 family inet >set interfaces gr-2/3/0 unit 0 family iso > >set protocols isis interface gr-2/3/0.0 point-to-point >set protocols isis interface gr-2/3/0.0 level 1 disable >set protocols isis interface gr-2/3/0.0 level 2 metric 1000 > > >-- > >Thanks for any thoughts or ideas. > >-M >_______________________________________________ >juniper-nsp mailing list juniper-nsp@puck.nether.net >https://puck.nether.net/mailman/listinfo/juniper-nsp _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp