[c-nsp] MTU on MPLS TE Tunnels w/PA-FE-TX?

[Rodney Dunn]

> I found some things in the archives about people complaining the PA-FE-TX is limited in hardware to 1500 byte MTU, but then I found other people saying it should work fine with MPLS tagged packets as long as you specify the size with tag-switching mtu or mpls mtu, which I have done without success. I know the PA-FE-TX will refuse to be configured manually for any other size MTU larger than 1500, so I'm leaning towards it being a hardware limitation. The tunnel interface even shows an MTU of 1496 in the output of show mpls interfaces detail. It initially appears to come up as 1514 but then drops to 1496.
>

CSCsc62963 [QDDTS] [CCO]
Internally found severe (Sev2) bug: Resolved (R)
Have configurable MTU Range 1500 -1530 on PA-1FE and PA-2FE

Fixed in 12.2(28)SB and 12.2(31)SB.

IIRC max SDU size is 1530 bytes on the wire.

TE is just a label stack and if it's native IP only 4 bytes.

I think you have something else wrong. 

What does your configurations look like and topology.

Rodney

 
> There isn't a whole lot of documentation on this other than use mpls mtu if you're using ethernet... Most MPLS documents assume you're using POS or Gig-e where you wouldn't really need to worry about it.
> 
> Can someone comment on this an indicate if there is a FastEthernet interface type on a 7200 that will support a larger MTU size for MPLS TE tunnels to pass 1500 byte packets or if there is a way to make the PA-FE-TX work and pass MPLS tagged packets larger than 1500 bytes? I know I could use the PA-GE but that quickly eats bandwidth points, or I could use NPE-G1 or NPE-G2 interfaces, but I don't have either engine presently and they are expensive propositions just to fix an MTU problem.
> 
> 
> Thanks for any insight!
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