LXE application not working after converting sites to MPLS from FR.

[ashokpatel]

We are in process of converting all over site to MPLS from Frame relay. Most of the applciation see better response. But One applciation by LXE ( for warehouse management,,using Cisco AP technology) can not run properly. ( Only at startup - It will not connect to server at remote cental site - using MPLS, Surprising when we try ti manually, It works fine. SO only at boot time it will not work.) we converted back to FrameRealy, every thing works great. The port,CIR/CAR etc are same.

[Harold Ritter]

Have you verified that the path MTU is at least 1500 bytes for the MPLS network? This might be the issue.

Try pinging from one CE router to the other (or even better from the workstation to the server if possible) using a 1500 bytes packet and disallowing fragmentation and see if the ping packets make it to destination and back.

Hope this helps,

[rais.ahmad]

Harold,

Can you please explain why it needs to be 1500.

Thanks.

[Harold Ritter]

It is simply because you want to make sure that you can transport a 1500 bytes frame, which is mainly used in internetworking these days, over the MPLS cloud given that 8 bytes (two labels) will be added to the original frame.

It seem like this wasn't the cause of the issue in this particular case though.

Hope this helps,

[rais.ahmad]

Thanks.

[ashokpatel]

We are able to resolve the issue. I used AF31 for all TCP port 2000-2002 ( somewhere along the path of Cisco IP phone implementation, I read to use these ports for AF31). LXE old scanning gun's TCP stack was using port 2002. and in ack. package we were marking the packet with AF31.LXE TCP stack rejected the packet.Once we apply the routinue DSCP (00) for those packets, it all worked fine.