[c-nsp] MPLS EXP field question

[Mikael Abrahamsson]

On Thu, 8 Apr 2010, Michael Robson wrote:

> Is it true that the when subsequent layers of labels are added to MPLS 
> traffic, the EXP field is copied to the top most label from the next one 
> downward (this is on a 6500 using LAN-based cards)?

Yes, that is generally the default when doing encapsulation, if there is 
any QoS information in the packet being encapsulated, then use that 
information for the encapsulation header. So IP prec->.1p and IP prec -> 
MPLS EXP (and .1p header if this is done over ethernet).

On a platform like the 6500 whichs not really a classic router, this isn't 
true in all cases. For full information you really have to order a 
document from cisco professional services that explains all corner cases 
in your perticular environment. There are quite a few commands that 
changes its behaviou and it's definitely not straight forward.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se