[j-nsp] Layer 2 VPNs and MTU
dermot at irishbroadband.ie
Wed May 3 07:26:39 EDT 2006
That's interesting alright - it appears that the vrf-mtu-check is enable
by default on the J4300s that we use at the CE, but not on the M-series
at the core. However, we don't add the loopback to the routing instances
for our L2VPNs, so there is no IP-enabled interface from which to send
the ICMP unreachables. I'll configure this up on our lab routers and see
how I get on - it should eliminate the need to reduce MTU on a
downstream router interface pair.
I don't think that this will help with the problem that we are having
though, unfortunately, which seems be occurring as a result of MS (and
others) essentially breaking PMTUD.
Thanks for your help,
On Wed, 2006-05-03 at 15:20 +0530, Arpit Mittal (GR/EIL) wrote:
> Hi Dermot,
> We have another command to ensure the path mtu ....
> This is applicable for traffic flowing via VRF, and applies globally to
> all the VRFs.
> chassis vrf-mtu-check
> help topic chassis vrf-mtu-check
> help reference chassis vrf-mtu-check
> I hope it will help.
> Arpit Mittal
> Ericsson India Private Limited.
> Tel : +91 124 256 08 08 / +91 124 508 08 08
> Fax: +91 124 256 54 54
> Mobile : +91 98713 74801
> E-mail : arpit.mittal at ericsson.com
> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net
> [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Dermot
> Sent: Wednesday, May 03, 2006 3:08 PM
> To: Fedorov, Konstantin
> Cc: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] Layer 2 VPNs and MTU
> Hi Konstantin,
> Thanks for the feedback - there doesn't seem to be an analogous command
> in JunOS. The ERX supports it, I think, but we don't have one :-(
> Also, as I intimated, getting the subscriber to change anything is
> something we're trying to avoid. The majority of our customers are not
> very computer literate and trying to get them to hack the registry to
> reduce MTU is a notion that would have our CSRs wailing and gnashing
> their teeth!
> On Wed, 2006-05-03 at 13:13 +0400, Fedorov, Konstantin wrote:
> > Hi,
> > Recently, I have the same problem with microsoft.com site.
> > But CPE was Cisco soho router.
> > The problem resolved when I configure Ip tcp adjust-mss 1452
> > Hope this will be useful.
> > I am beginner with juniper, so I couldn't give you equivalent command
> > in the junos.
> > -----------------------
> > Sincerely Yours,
> > Konstantin Fedorov
> > -----Original Message-----
> > From: juniper-nsp-bounces at puck.nether.net
> > [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Dermot
> > Williams
> > Sent: Wednesday, May 03, 2006 12:38 PM
> > To: juniper-nsp at puck.nether.net
> > Subject: [j-nsp] Layer 2 VPNs and MTU
> > Hi,
> > Hope some of you can give me some pointers on the above issue. We're
> > in the process of deploying a significant change to our architecture.
> > Some of this target architecture will rely on the use of Layer 2 VPNs
> > to deliver subscribers to a Redback. Unfortunately we're hitting some
> > roadblocks in the form of MTU and Path MTU Discovery.
> > The most obvious solution to our problem is to increase the MTU across
> > our network but unfortunately that isn't an option because many of the
> > links that we use for backhaul don't support jumbo frames. Asking our
> > subscribers to decrease their MTU is a non-runner as well for customer
> > support reasons.
> > We've reduced the MTU on the next-hop interfaces for our subscribers
> > and this has alleviated some of the issues but some sites
> > (http://www.microsoft.com/) don't seem to support PMTUD properly, so
> > they are still problematic. I'm hoping and assuming that others have
> > come across similar issues - PPPoE, for example, should present the
> > same challenge - so I'd appreciate if someone could give me a heads up
> > on how they circumvented this problem - if at all.
> > TIA
> > Dermot Williams
> > Senior Network Engineer
> > Irish Broadband Internet Services Ltd.
> > _______________________________________________
> > juniper-nsp mailing list juniper-nsp at puck.nether.net
> > http://puck.nether.net/mailman/listinfo/juniper-nsp
> Dermot Williams
> Senior Network Engineer
> Irish Broadband Internet Services Ltd.
> juniper-nsp mailing list juniper-nsp at puck.nether.net
Senior Network Engineer
Irish Broadband Internet Services Ltd.
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