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File access failing over MPLS circuit

I am experiencing an intermittent problem when accessing files across an MPLS cloud.  Specifically, the errors occur in any of the three following scenarios:

1.  Remote users attempting to access files at their local office via remote VPN.  VPN is terminated at HQ concentrators first, users then traverse MPLS cloud to local office.

2.  Local users traverse MPLS cloud from local office to HQ file servers.

3.  Users at HQ attempting to access files at local office across MPLS cloud.

The errors that we are running into vary from write failures upon opening remote files, to transfers stalling, to transfers terminating, to file inaccessible errors.

Topography -  (local/remote office server) - (rack switch) - (router + MPLS) - (AT&T demark) (MPLS Cloud) - (demark) - (router + MPLS) - (switch) - (HQ office)

The MTU sizes vary between the two head end routers - one is 1470 and the other is 1524 - would this have an impact end to end or am I correct in my understanding that MTU size only matters to next hop?

At this point I have isolated the issue to the router itself, however, being intermittent (meaning I don't hear about an occurence until the day after it happens) I am having a problem gathering data on the issue for troubleshooting.

My question is essentially this - has anyone else here experienced similar or like problems who is willing to point me in the right direction or able to give me likely sources to begin checking?

Thanks
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atlas_shuddered
Asked:
atlas_shuddered
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2 Solutions
 
dineeshCommented:
hi,

have you checked for the CRC, interface resets and the I/O errors on the routers?
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logic2Commented:
try to do an extended ping test between the local office and the HQ office, while at the same time monitoring the CRCs.
Also as per Dineesh try to monitor the CRC errors, for example take a snap shot of them and once you are advised that there was a problem have another look usually the stuff u r mentioning are line problems
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atlas_shudderedSr. Network EngineerAuthor Commented:
Sorry so long to post back.

Have checked and not seeing CRC's occur in line with access failures.  Am currently looking at MTU, MSS and PMTUD over the link as it seems to only be occuring (revelation) among VPN users.  Access is fine at local office and remote (intranetwork) sites.  Only when it comes across the VPN concentrators.
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logic2Commented:
hmmm i dont like VPN stuff so i wont be able to help if it comes to that :)
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atlas_shudderedSr. Network EngineerAuthor Commented:
Changed MTU on interface, didn't see CRC errors when troubleshooting but thanks for the input nonetheless.
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