[c-nsp] Best practice, MPLS and MTU settings

Xu Hu jstuxuhu0816 at gmail.com
Sun Oct 27 08:02:08 EDT 2013

any particular reason for this?
I meant you set 9192 & 9178? did you consider the mpls stack labeles or
Layer 2 headers? or whatever, then finally you made this recommendation

On Saturday, October 26, 2013, Mark Tinka <mark.tinka at seacom.mu> wrote:
> On Friday, October 25, 2013 04:39:57 AM Nick Hilliard wrote:
>> I aim towards a 9100 byte ip mtu, in order to guarantee a
>> 9000 byte MTU for customers with plenty of overhead on
>> our side.  Sometimes this isn't possible due to third
>> party provider core link restrictions.
> We are a Cisco and Juniper house.
> To match things, we run 9,192 bytes on Juniper and IOS XR-
> based Cisco platforms, as well as 9,178 bytes on IOS and IOS
> XE-based Cisco systems.
> We have noted that some Juniper SDH/SONET line cards require
> you to set the MTU at the address family level (inet, inet6,
> iso and mpls) for the MTU to take effect. You'd normally
> apply it at the global interface level and each address
> family would infer what it needs, but not on SDH/SONET line
> cards. This issue does not affect Ethernet line cards.
> Cisco FE ports tend to not support Jumbo frames (except
> SPA's on the XR 12000 and CRS systems), but Juniper have no
> issue supporting Jumbo frames on FE ports. Suffice it to
> say, I haven't used FE ports anywhere for nearly 5x years
> now.
> Several Cisco switches will top out at 9,000 bytes. Not much
> you can do about that if you have them. However, newer
> platforms shipping now do up that to be inline with what we
> prefer now.
> Mark.

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