[c-nsp] Mpls on fastethernet <-> atm route-bridge ip link?

Sean Watkins sean at northrock.bm
Thu Feb 9 18:23:18 EST 2006

>>  ip pim sparse-dense-mode
>>  atm route-bridged ip
>>  tag-switching mtu 1508
>>  pvc 80/50
>>   tx-ring-limit 3
> Yes, I have this kind of setup. It's been happily running for
> something like two years, with no MTU problems, both sides acting both
> as P routers and PE routers (so I'm quite certain the labels go
> through OK).

I wonder if the atm route-bridge ip command causes it to fail?

What exactly is the difference from atm route-bridged ip and the  
aal5snap command? Both are RFC1483 right?

>  tag-switching mtu 1530
>  tag-switching ip
>  pvc xxx/xxx

I attemped to change my config, to be the same as yours, and I  
couldn't get data working. I stuck an access list on the port, and I  
could see frames coming in, from the fastethernet side to the atm  
side, but I couldn't ever get data from the ATM side going back to  
the ethernet port.

> The encapsulation has to be OK between your ATM interface and the
> converter, so you can't just change them, but I think that the choice
> of encapsulation might impact the labels. If the labels weren't going
> through I'd have advised you to test aal5snap since it works for me.

I'm asking the service provider what they are using; according to a  
quick conversation I had this afternoon he can't change the aal5snap  
on the fastethernet port only on the atm side? if that makes any sense?

> It dies because your ip mtu is 1500.
> To see if jumbo frames go through, don't worry about MPLS (turn it
> off!) and try setting the ip mtu to 1508 on both interfaces.

Yah I can't change it.. I get this message:

Rtr(config-if)#mtu 1503
% Interface FastEthernet5/0 does not support user settable mtu.

Rtr(config-if)#ip mtu 1503
% Invalid input detected at '^' marker.

Rtr(config-if)#ip mtu ?
   <68-1500>  MTU (bytes)

Rtr(config-if)#ip mtu

>> The service providers fastethernet port is attached to a Newbridge/ 
>> Alcatel
>> 36170 - anyone have any experiencing using jumbo frames on that gear?
> Mine is made by Ericsson, but I'd be very surprised if your Alcatel
> wasn't capable of at least 1518 (for vlans). Maybe it's simply that
> your service provider simply set the mtu on the port to 1500!

Who knows!


More information about the cisco-nsp mailing list