[j-nsp] MTU problems over VPLS

[Luca Salvatore]

Thanks for the info.
I have managed to fix it by tweaking the MTU on my 10Gb interfaces between P routers.

I set the interface MTU to be 1548
Then set the family mpls MTU to be 1522

This seems to have helped.

Luca

From: david.roy at orange.com [mailto:david.roy at orange.com]
Sent: Wednesday, 13 February 2013 8:33 AM
To: Luca Salvatore
Cc: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] MTU problems over VPLS

We hit this PR but should be fixed in your release. Double check with JTAC if there is no regression or corner case?

David

Problem Report

Number

PR568550

Title

With default settings,4 bytes lesser ip payload can be sent when MX-80 is acting as P router compared to M7i

Release Note


MPLS MTU was reserving 3 labels length apart from the MPLS labels that come in the packet. So due to this the packets were getting dropped in P router when ping packet size was 1456B for physical MTU of 1514B(excludes CRC).


Severity

Major

Status

Closed

Last Modified

2012-09-11 23:47:31 PDT

Resolved In

10.4R5 11.1R3 11.2R1 11.3R1

Operating System

Junos

Product

MX-series

Functional Area

software

Feature Group

Platform and Infrastructure

Workaround


Set higher MTU i.e.(X+12Bytes) in order to allow X bytes.


Triggers

* Trio platform * sending packet more than 1455B


Envoyé de mon iPad

Le 12 févr. 2013 à 22:25, "Luca Salvatore" <Luca at ninefold.com<mailto:Luca at ninefold.com>> a écrit :
11.2R5.4 on all MX involved - this was the recommended release up to a few days ago.
Any ideas on the PR number?

Luca


-----Original Message-----
From: david.roy at orange.com<mailto:david.roy at orange.com> [mailto:david.roy at orange.com]
Sent: Wednesday, 13 February 2013 8:24 AM
To: Luca Salvatore
Cc: juniper-nsp at puck.nether.net<mailto:juniper-nsp at puck.nether.net>
Subject: Re: [j-nsp] MTU problems over VPLS

Which release do you use ? Experienced some mpls mtu issue on trio platform. Known PR...

Envoyé de mon iPad

Le 12 févr. 2013 à 22:17, "Luca Salvatore" <Luca at ninefold.com<mailto:Luca at ninefold.com>> a écrit :


I have a few sites connected via a VPLS core.  The core devices are all MX 10 routers connected via 10Gb fibre.
I'm having problems doing file copies (SCP between two Centos VMs).

The issue is that the file copy never gets anywhere, on the Centos CLI it sits at 0% then says 'stalled'
To fix this issue I have just set the MTU on the Centos machines to be 1400 - when this is in place the copy works and I get nice speeds.

I don't believe I should have to modify the MTU though, shouldn't path MTU discovery take care of this?

For example - I have done some TCPdumps, I can see the sender is sending traffic with the DF bit set, however I don't see any 'ICMP fragmentation needed' coming back from the MX saying the MTU is too big, I assume this should be the case.

I haven't modified any of the MTU's on the MX, everything is just the default.

I also have normal layer 3 running over the fibre between the routers and when I use that I don't see any issues, so it must be something to do with VPLS.

Any thoughts would be greatly appreciated.

Thanks
Luca.

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Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc

pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler

a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,

France Telecom - Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.



This message and its attachments may contain confidential or privileged information that may be protected by law;

they should not be distributed, used or copied without authorisation.

If you have received this email in error, please notify the sender and delete this message and its attachments.

As emails may be altered, France Telecom - Orange is not liable for messages that have been modified, changed or falsified.

Thank you.