2. Use the ping Command to Verify MPLS Labels

Purpose

On the egress router (the router receiving the MPLS echo packets), you must configure the address 127.0.0.1/32 on its loopback (lo0) interface, resulting in echo requests being sent as MPLS packets destined for the address 127.0.0.1 and the well-known port 3503. When the echo request arrives at the egress router, the receiver checks the contents of the packet and sends a reply containing the correct return value. The sender of the echo request waits 2 seconds for the echo reply, then times out. In the example network shown in Figure 5, the egress router is R6. If address 127.0.0.1/32 is not configured, the egress router does not have this forwarding entry and therefore simply drops the incoming MPLS pings and replies with "ICMP host unreachable" messages.

Action

To verify MPLS labels, follow these steps:

1. On the egress router, in configuration mode, go to the following hierarchy level:

[edit]

user@egress-router# edit interfaces lo0 unit number

2. Configure the loopback (lo0) interface with the following IP address:

[edit interfaces lo0 unit number]

user@egress-router# set family inet address 127.0.0.1/32

3. Verify the configuration:

user@egress-router# show

user@egress-router# commit

4. On the ingress router, in operational mode, enter the following command to ping the egress router:

user@ingress-router> ping mpls rsvp lsp-name detail

Sample Output 1

user@R6> edit

Entering configuration mode

[edit]

user@R6# edit interfaces lo0 unit 0

[edit interfaces lo0 unit 0]

user@R6# set family inet address 127.0.0.1/32

[edit interfaces lo0 unit 0]

user@R6# show 

family inet {

    address 10.0.0.6/32;

    address 127.0.0.1/32;

}

family iso {

    address 49.0004.1000.0000.0006.00;

}

[edit interfaces lo0 unit 0]

user@R6# commit

commit complete

Sample Output 2

user@R1> ping mpls rsvp R1-to-R6 detail 

Request for seq 1, to interface 69, label 100064

Reply for seq 1, return code: Egress-ok

Request for seq 2, to interface 69, label 100064

Reply for seq 2, return code: Egress-ok

Request for seq 3, to interface 69, label 100064

Reply for seq 3, return code: Egress-ok

Request for seq 4, to interface 69, label 100064

Reply for seq 4, return code: Egress-ok

Request for seq 5, to interface 69, label 100064

Reply for seq 5, return code: Egress-ok

--- lsping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

What It Means

Sample Output 1 from egress router R6 shows that the IP address 127.0.0.1/32 is configured.

Sample Output 2 from ingress router R1 shows that an echo request is sent with a label (100064), indicating that the echo requests were sent over the LSP R1-to-R6.