[c-nsp] strange behavior over MPLS network - remote desktopwon't work

[Chris Hale]

On Sun, May 31, 2009 at 8:38 PM, Terry Baranski <tbaranski at mail.com> wrote:

> > On Sun, May 31, 2009 at 8:03 PM, Chris Hale wrote:
> >
> > I'm using PA-FE-TX as you guessed.  I have enabled the larger
> > MTUs for MPLS
> > with mpls mtu 1538 as per others who have successfully used this.
> >
> > I'm using one of my J2320's (CE router) and found this:
> >
> > ping do-not-fragment detail size 1473 192.168.3.254
> > PING 192.168.3.254 (192.168.3.254): 1473 data bytes
> > ping: sendto: Message too long
> >
> > ping do-not-fragment detail size 1472 192.168.3.254
> > PING 192.168.3.254 (192.168.3.254): 1472 data bytes
> > 1480 bytes from 192.168.3.254 via ge-0/0/3.600: icmp_seq=0 ttl=62
> > time=12.598 ms
> > 1480 bytes from 192.168.3.254 via ge-0/0/3.600: icmp_seq=1 ttl=62
> > time=14.612 ms
> >
> > What does that indicate to you?  1472 + VLAN tag plus MPLS < 1500?
>
> When you ping from a Juniper, the packet size that you specify doesn't
> include overhead.  So once you add IP (20 bytes) and ICMP (8 bytes) to the
> above, a ping of 1472 is really a ping of 1500.  Therefore 1473 wouldn't be
> expected to work if all links on the path have an IP MTU of 1500.
>
> Which CE is the above ping from?  Is it testing the end-to-end path that
> isn't working?  If so the MTU seems fine (now).  If RDP still isn't working
> maybe you can post the capture.
>
> This is pinging from the CE at Site B to Site W.  Yes, it is testing the
end-to-end path that doesn't carry the RDP traffic.

I will be capturing traffic at the POP before it hits the PE tomorrow.  I'll
post for all to see in both binary Wireshark format and plain text.

Thanks,
Chris

-- 
------------------
Chris Hale
chale99 at gmail.com