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[jsmith9]

(QID:AR072) Which label operation are performed by a label edge router?
"correct answer: PUSH and PHP"
I believe this answer to be incorrect, if you read the link included in the answer it states " In certain cases, the MPLS label stack is popped off the packet header at the hop before the egress LSR. This process is called Penultimate Hop Popping (PHP). By using PHP, transit routers that are connected directly to the egress LSR can effectively offload the CPU load on that router by popping the last label themselves and forwarding the packet."

The hop before an egress LSR ie LER (PE) would be a LSR (P). From my understanding an LER or egress LSR would preform only PUSH/POP.

Also, if you look at question (QID:AR062) the answer "performs penultimate hop popping" is correct under Label Switch Router and not Label Edge Router".


https://www.cisco.com/c/en/us/td/docs/sw...rview.html
Label Disposition
.i.label disposition;

.i.MPLS:label disposition;

On the egress LSR at the provider edge (PE), the MPLS label stack is popped off the packet header leaving an IPv4 or IPv6 packet to be forwarded onward. This process is called disposition.

In certain cases, the MPLS label stack is popped off the packet header at the hop before the egress LSR. This process is called Penultimate Hop Popping (PHP). By using PHP, transit routers that are connected directly to the egress LSR can effectively offload the CPU load on that router by popping the last label themselves and forwarding the packet.

.i#.penultimate hop popping, see PHP;

.i.PHP;