Discovering Lsp Breakage; Mpls Basic Configuration Guide, Cisco Ios Xe Everest 16.5.1 (Cisco Asr 900 Series - Cisco ASR 900 Series Manual

MPLS LSP Ping, Traceroute, and AToM VCCV
OutLabel : FastEthernet0/0/0, 22
RSVP Signalling Info:
RSVP Path Info:
My Address: 10.131.191.230
Explicit Route: 10.131.191.229 10.131.159.226 10.131.159.225 10.131.159.251
Record
Tspec: ave rate=512 kbits, burst=1000 bytes, peak rate=512 kbits
RSVP Resv Info:
Record
Fspec: ave rate=512 kbits, burst=1000 bytes, peak rate=512 kbits
Shortest Unconstrained Path Info:
Path Weight: 20 (TE)
Explicit Route: 10.131.191.230 10.131.191.229 10.131.159.226 10.131.159.225
History:
Tunnel:
Time since created: 9 days, 14 hours, 12 minutes
Time since path change: 2 minutes, 18 seconds
Current LSP:
Uptime: 2 minutes, 18 seconds
Prior LSP:
ID: path option 1 [3]
Removal Trigger: tunnel shutdown
A trace mpls command issued at PE1 verifies that packets with 22 as the outermost label and 19 as the end
of stack label are forwarded from PE1 to PE2.
Device# trace mpls ipv4 10.131.159.252/32
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not transmitted,
Type escape sequence to abort.
0 10.131.191.230 MRU 1496 [Labels: 22/19
Exp: 0/0]
R 1 10.131.159.226 MRU 1504 [Labels: 19 Exp: 0] 40 ms
R 2 10.131.159.229 MRU 1504 [implicit-null] 28 ms
! 3 10.131.159.230 40 ms
The MPLS LSP Traceroute to PE2 is successful, as indicated by the exclamation point (!).

Discovering LSP Breakage

A Label Distribution Protocol (LDP) target-session is established between devices PE1 and P2, as shown in
the output of the following show mpls ldp discovery command:
Device# show mpls ldp discovery
Local LDP Identifier:
10.131.191.252:0
Discovery Sources:
Interfaces:
Targeted Hellos:
Enter the following command on the P2 device in global configuration mode:
Device# no mpls ldp discovery targeted-hello accept
The LDP configuration change causes the targeted LDP session between the headend and tailend of the traffic
engineering (TE) tunnel to go down. Labels for IPv4 prefixes learned by P2 are not advertised to PE1. Thus,
Src 10.131.191.252, Dst 10.131.159.251, Tun_Id 1, Tun_Instance 28
Route: NONE
Route: NONE
10.131.159.251
'.' - timeout, 'U' - unreachable,
'R' - downstream router but not target
GigabitEthernet0/0/0 (ldp): xmit/recv
LDP Id: 10.131.191.251:0
Tunnel1 (ldp): Targeted -> 10.131.159.251
10.131.191.252 -> 10.131.159.252 (ldp): active/passive, xmit/recv
LDP Id: 10.131.159.252:0
10.131.191.252 -> 10.131.159.251 (ldp): active, xmit/recv
LDP Id: 10.131.159.251:0

MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)

ICMP ping and trace Commands and Troubleshooting
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