[j-nsp] Jumbo frames / mismatch MTU

[aaron1 at gvtc.com]

Yeah, crazy how there's many mtu differences...apparently cosmetic since we
all know ethernet always has a header !

IOS (classic and XE) doesn't include eth header

IOS-XR like MX - does include eth header

For some reason on my MX104's I did...
set interfaces ae10 mtu 9192

here's some things I've flipped on acx5048 for interfaces and vpls or
l2circuits....

set interfaces ge-0/0/47 mtu 9216

set protocols l2circuit neighbor 10.10.10.3 interface ge-0/0/47.100 mtu 1500

set routing-instances 500 protocols vpls mtu 9216

you can ignore mtu in ospf, although, I prefer to fix instead of ignore.

Also, I recall having something weird, where I ospf neighbored over a 3rd
part tls service, and when they made changes to the transport, that my ospf
started having issues establishing neighborship

(also, your mention of ldp dropping, probably has everything to do with
broken ospf, as I understand ldp needs to the /32 loopbacks to fully
establish... the initial ldp is link local mcast, but the ldp step 2 is a
tcp session to the adjacent loopbacks... hence IGP must be up)

-Aaron