Packet Flow Example For The Trace Mpls Command - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x BGP and MPLS Configuration Guide
host1:pe1#ping mpls ip 10.2.2.2/32 detail
Sending 5 UDP echo requests for LDP IPv4 prefix, timeout = 2 sec
Sending MPLS ping echo request, handle 8073311 seq 21241
! 10.2.2.2 Replying router is an egress for the FEC at stack depth/0 seq 21241
Sending MPLS ping echo request, handle 8073311 seq 21242
! 10.2.2.2 Replying router is an egress for the FEC at stack depth/0 seq 21242
Sending MPLS ping echo request, handle 8073311 seq 21243
! 10.2.2.2 Replying router is an egress for the FEC at stack depth/0 seq 21243
Sending MPLS ping echo request, handle 8073311 seq 21244
! 10.2.2.2 Replying router is an egress for the FEC at stack depth/0 seq 21244
Sending MPLS ping echo request, handle 8073311 seq 21245
! 10.2.2.2 Replying router is an egress for the FEC at stack depth/0 seq 21245
Success rate = 100% (5/5), round-trip min/avg/max = 4/4/0 ms

Packet Flow Example for the trace mpls Command

The following example illustrates the packet flow that results when you issue the
trace mpls ip command from router PE 1 (10.1.1.1) to router PE 2 (10.2.2.2) over
an LDP base tunnel.
1.
2.
372
Packet Flow Examples for Verifying MPLS Connectivity
MplsNextHopIndex 32 handle 8073311
'!' - success, 'Q' - request not transmitted,
'.' - timeout, 'U' - unreachable,
'R' - downstream router but not destination
'M' - malformed request, 'N' - downstream router has no mapping
host1:pe1#trace mpls ip 10.2.2.2/32
PE 1 sends an MPLS echo request UDP packet that contains an LDP IPv4 sub-TLV
and a Downstream Mapping TLV. The packet has the following attributes:
Source address 10.1.1.1
Destination address 127.0.0.0/8
UDP port 3503
TTL 1
IPv4 prefix in the TLV 10.2.2.2/32
Sender's handle Randomly generated 32-bit number used to match the reply
Sequence number Integer that is incremented for each echo request packet
The TTL expires on router P 1. P 1 exceptions the packet up to the control plane.
Router P 1 then creates an MPLS echo reply packet in reply to the received MPLS
echo request. The MPLS echo reply packet has a return code of 8, which means
that the packet would have been label-switched at the outermost label (label-stack
depth 1). The Downstream Mapping TLV is set to indicate the path that the packet
would have taken from the router. The Interface and Label Stack TLV is included