[frr] 2 MPLS Questions

Renato Westphal renato at opensourcerouting.org
Sat Mar 18 08:45:45 EDT 2017

On Sat, Mar 18, 2017 at 2:27 AM, Roopa Prabhu <roopa at cumulusnetworks.com> wrote:
> On 3/17/17, 10:19 PM, Vivek Venkatraman wrote:
>> This is correct. By definition, if a router is the penultimate hop, it
>> means the actual egress is downstream and has signaled (advertised) an
>> implicit-null label to this router. The router doing the PHP knows the next
>> hop to forward to (the egress) without doing any additional lookup.
>> This behavior should already be supported.
>> What is not supported (if I remember right) is the ability on the egress to
>> terminate a label and perform a (route) lookup.  That is needed to really
>> be able to support any L2/L3 VPN service properly.
> yes, correct. terminating a label and performing a route lookup is not supported
> today.

The exception being the ipv4/ipv6 explicit null labels. Please take a
look: https://github.com/torvalds/linux/blob/master/net/mpls/af_mpls.c#L1872

Renato Westphal

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