[j-nsp] MPLS issue

[David Ball]

  We do the same here.  1600 on cust ports, 9k on core network ports.
Shouldn't have to revisit them too often.

David


On 03/03/2008, Erdem Sener <erdems at gmail.com> wrote:
> FWIW, I'd configure all ethernets with MTU 1600 as a policy and never
> think about MTU again.
> (including any switches in the middle as said)
>
> Erdem
>
> On Mon, Mar 3, 2008 at 5:11 PM, Mark Tinka <mtinka at globaltransit.net> wrote:
> > On Monday 03 March 2008, Ying Zhang wrote:
> >
> >  > we are having a wired MPLS problem. Here is how the
> >  > network looks like:
> >  >
> >  > end users ---- M7i ---- M120 ----ISP
> >  >
> >  > The mpls lsp is between M7i and M120. The problem is the
> >  > end users have problems accessing certain websites, very
> >  > slow or not accessible, some websites no problem at all.
> >  > With MPLS disabled (OSPF only), the problem is gone. I
> >  > think it is a MTU issue, tried to lower MTU on M7i user
> >  > side, didn't fix it. Might also try to increase MTU  on
> >  > MPLS interfaces, but not sure. Any thoughts? Very
> >  > appreciated.
> >
> >  Yes, definitely sounds like an MTU issue.
> >
> >  For a single label (MPLS switching only, no VPN's or
> >  anything kinky like that), you need at least 1504 bytes on
> >  Ethernet.
> >
> >  With L3VPN's, you need 2 labels (one for the VPN and another
> >  for MPLS switching). This brings you to 1508 bytes.
> >
> >  To this end, I've normally configured 1524 bytes at a bare
> >  minimum on the interface. Note, however, that both the
> >  router port and adjacent Ethernet switch need to be
> >  configured for higher MTU's, otherwise you'll experience
> >  the symptoms you describe above.
> >
> >  Cheers,
> >
> >  Mark.
> >
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> >
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