[c-nsp] switching off MPLS penultimate pop hopping

[Oliver Boehmer (oboehmer)]

>>>  Is there any possibility to force particular Cisco PE router to
>>>  perform the FIB lookup in addition to LFIB lookup during during
>>>  packet forwarding from MPLS interface to CE?
>>> 
>>>  As far I understand it means to disable 'MPLS penultimate pop
>>> hopping'.
>> 
>> enable "mpls ldp explicit-null" on the edge-LSR to advertise an
>> explicit-null instead of the implicit-null/pop.
>> 
>> Why do you want/need this? Usually folks only use it to provide QoS
>> transparency/DS tunneling through an MPLS core..
> 
> I have multiply CE routers connected to PE over single subnet.
> CEs are running IGP between each other, some CEs (core routers) also
> advertise aggregate route. PE redistributes only aggregate route to
> MP-BGP. 
> 
> Right now all label switched packets destinated to any of customer
> subnets will be routed to CE core routers, ignoring more specific
routes in
> PE FIB. 
> 
> I would like to avoid such suboptimal routing on PE-CE edge and
> perform FIB lookup on PE.

Oh, MPLS-VPN. Then advertising explicit-null doesn't help since the
packet arrives labelled already. I misunderstood your question.
You want the VPN label advertised via MP-BGP to be a so called
"aggregate-label" (which forces another fib lookup after disposition),
and (I think) the only way to force this is to have the PE aggregate and
thus originate the summary prefix, rather than the "core" CE. Prefixes
advertised by the CE's will not get an aggregate label.

	oli