'R' - downstream router but not destination
'M' - malformed request, 'N' - downstream router has no mapping
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.
host1:pe1#trace mpls ip 10.2.2.2/32
1. 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:
10.1.1.1Source address
127.0.0.0/8Destination address
3503UDP port
1TTL
10.2.2.2/32IPv4 prefix in the TLV
Randomly generated 32-bit number used to match the replySender’s handle
Integer that is incremented for each echo request packetSequence number
2. 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 in
the echo reply packet. The MPLS echo reply packet is sent back as a labeled UDP
packet with the following attributes:
10.3.3.3Source address
10.1.1.1Destination address
3503UDP port
375Copyright © 2010, Juniper Networks, Inc.
Chapter 5: Monitoring MPLS
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