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MPLS question

I have a question about the "show mpls ip binding" command.

r2#show mpls ip binding

5.5.5.0/24

in label: 17

out label: imp-null lsr: 10.0.0.1:0 inuse

6.6.6.0/24

in label: 18

out label: 17 lsr: 10.0.0.1:0 inuse

10.0.0.0/24

in label: imp-null

out label: imp-null lsr: 10.0.0.1:0

10.0.1.0/24

in label: imp-null

out label: 16 lsr: 10.0.0.1:0

10.9.9.0/24

in label: 16

out label: imp-null lsr: 10.0.0.1:0 inuse

is the subnet 5.5.5.0/24 the destination network, or is 10.0.0.1 the destination from 5.5.5.0?

Thanks,

John

HTH, John *** Please rate all useful posts ***
1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Bronze

Re: MPLS question

No, 10.0.0.1 seems to be the adjacent router on the path towards 5.5.5.0/24.

The packet is coming in as label in R2 (label 17) and leaving as an IPv4 towards 10.0.0.1

10.0.0.1 receives this packet as a regular IPv4 packet and performs the necessary routing on it.

The imp-null is a way for 10.0.0.1 to tell R2 to pop the top label and send the packet as IPv4.

HTH,

__

Edison.

6 REPLIES
Hall of Fame Super Bronze

Re: MPLS question

5.5.5.0/24 is on 10.0.0.1 IPv4's routing table. A PHP was sent from this router to R2.

HTH,

__

Edison.

Re: MPLS question

Can you expand on your answer a little Edison? From the way that I'm reading your response, it seems as though the "show mpls ip binding" was done on the 10.0.0.1 router. Is this correct?

John

HTH, John *** Please rate all useful posts ***
Hall of Fame Super Bronze

Re: MPLS question

No, 10.0.0.1 seems to be the adjacent router on the path towards 5.5.5.0/24.

The packet is coming in as label in R2 (label 17) and leaving as an IPv4 towards 10.0.0.1

10.0.0.1 receives this packet as a regular IPv4 packet and performs the necessary routing on it.

The imp-null is a way for 10.0.0.1 to tell R2 to pop the top label and send the packet as IPv4.

HTH,

__

Edison.

New Member

Re: MPLS question

hi john,

here the network 10.0.0.1 is the network which is owned by #r2

here we can say 5.5.5.0 is destination,

in any mpls enabled router it assigns label to each and every route , but it does not assign any label to it's own routes , simply it assigns imp-null

thanks and regards

............ Ajay krishna

Re: MPLS question

Ajay,

I was under the impression that imp-null had nothing to do with the routers "own routes", but it was when PHP was in effect. The imp-null value is CoS value 3, and it tells the router to pop the label before it gets to its next hop which is the edge LSR. The edge LSR won't have to do two lookups when PHP is in effect. It only has to look up in its routing table on how to send the packet.

Am I wrong?

Thanks,

John

HTH, John *** Please rate all useful posts ***
Hall of Fame Super Bronze

Re: MPLS question

John,

You are spot on and thanks for the rating :)

__

Edison

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