[c-nsp] MPLS MTU

[Sergio D.]

Hello folks,

Some of our customers recently ran into some problems browsing and
pinging with over 1468. We fixed the browsing issue by adjusting MSS
on the incoming interfaces. It turns out that our core tag-switching
interfaces were set at the default 1500 which in turn allowed only a
1496 or 1492 IP payload depending on how many labels.
 So now we are changing the MPLS mtu to 1508, but on Cisco's website
it mentions the following :
"Setting the MPLS MTU to a high number can lead to packets being
dropped on some devices, because the labeled packet is larger than the
interface physical MTU."

A lot of our core is FE interfaces, I don't have a way to test this
before, wouldn't just automatically raise the physical MTU?
So after raising this an FE MTU goes to 1526? 1508 MPLS + 18 Vlan +
ethernet header?
Thanks,

-- 
Sergio Danellli
JNCIE #170