[j-nsp] MPLS CCC on EX4200

[Alexandre Snarskii]

On Thu, Jul 30, 2009 at 09:22:18AM +0100, Matthew Walster wrote:
> I'm trying to set up a point-to-point link between two sites using EX4200s,
> joining several ports at one site to several ports at the other site. It
> seems like the ideal way to do this would be with a layer 2 encapsulation
> technique such as CCC, tied in with MPLS - especially if the system was
> expanded to multiple sites.
> I have configured this with RSVP for label distribution, and OSPF for
> loopback distribution. When the link between the two sites comes up, it
> takes quite a while (more than a minute) for the MPLS labels to be
> distributed, but I presume this is either "normal behaviour" or I need to
> set something to speed this up. That's not my problem, however.
> 
> The intermediate link is a plain old standard ethernet circuit. When I

Have you tried to raise MTU on that ethernet circuit ? :) 

Something like: 

interface ge-A/B/C { 
  mtu 9012;
  unit 0 { 
      family inet { 
         mtu 1500;
         address ..... ;
      }
      family mpls { 
         mtu 4470;
      }
  }
}

actual numbers for interface and mpls mtu's may vary, but if you're
trying to achieve CCC connections it MUST NOT be less than 1540: 
1518(inner ethernet frame) + 4 (mpls label) + 18 (outer ethernet header).

> connect two laptops, one to each end of the MPLS circuit, then can ping each
> other fine. They can't seem to do HTTP traffic. I can login with WinSCP but
> it won't download the directory listing. Running several pings from the
> Windows laptop tells me that the maximum buffer size it can use is 1458,
> leading me to believe that this is an MTU issue, and the packets aren't
> being fragmented correctly.

Those packets are ethernet, and ethernet packets cannot be fragmented
easily... That's why you must run raised MTU on every MPLS link. 

> 
> Is there a common solution to this problem? Any advice appreciated.
> 
> Matthew Walster
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