MPLS behavior in multipoint interfaces

Hi team,

Today I ran into a "weird" behavior when enabling MPLS in a multipoint
environment. The summarized topology is as follows:

R1------------| |-------------------R3
                    | FRAME-RELAY |
R2------------| |-------------------R4

Physical interfaces (multipoint) are used on all routers and there is
a full mesh of PVCs among all routers. I enabled MPLS on the
interfaces of R4 and R2, but not on R3 and R1, thus traffic sent from
behind R1 or R3 that needs to reach a destination behind R2 or R4 will
be sent untagged. Since R2 and R4 interfaces are MPLS enabled I would
expect them to drop any untagged packets arriving at them; however
traffic traverses successfully and is able to get to its destination,
so this keeps thinking what is the expected behavior of MPLS in
multipoint interfaces. Any pointers are really appreciated.

Thanks,
Jorge

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Received on Sun May 16 2010 - 22:23:25 ART