Zte ZXR10 ZSR V2 Configuration Manual (System Management page 171

In the Echo Reply packet, the return code is 6, which indicates that the node is
an intermediate node. According to the return code, LSR1 knows that the packet
did not reach the destination.
6. LSR1: After receiving the Echo Reply packet from LSR3, LSR1 knows the
address and label information on LSR3. According to the return code, LSR1
knows that the packet did not reach the destination. LSR1 sends an MPLS Echo
Request packet to LSR2 again. The destination is the FEC on LSR4.
In the Echo Request packet, the TTL value in the MPLS header is 3, the
destination address in the IP header is 127.0.0.1, and both the source port
number and destination port number in the UDP header are 3503.
7. LSR2: After receiving the Echo Request packet whose TTL value is 3, LSR2
searches for label information and then forwards the packet to LSR3. The TTL
value decrements by one.
8. LSR3: After receiving the Echo Request packet whose TTL value is 2, LSR2
searches for label information and then forwards the packet to LSR4. The TTL
value decrements by one.
9. LSR4: After receiving the request packet packet whose TTL value is 1, LSR4
processes the packet. It finds that itself is the destination. Therefore, LSR4
responds to LSR1 with an MPLS Echo Reply packet.
In the Echo Reply packet, the return code is 3, which indicates that the node is
the destination node.
After the procedure, LSR1 knows the address and label information on LSRs along
the LSP.
Configuration Commands
To configure LSP trace on the ZXR10 ZSR V2, run the following commands:
Command
trace mpls ipv4 <ip-address><mask-length>[output-interf
ZXR10#
ace <interface-name>][destination <start-ipv4-address>[<end-ip
v4-address>][<increment>]][ttl <ttl>| timeout <timeout>| source
{<source-ipv4-address>|<source-ipv6-address>}|[{ddmap|dsmap}]]
trace mpls traffic-eng te_tunnel <id>[{master|slave}][ttl
ZXR10#
<ttl>| timeout <timeout>| source {<source-ipv4-address>|<source-ip
v6-address>}|[{ddmap|dsmap}]]
trace mpls pseudowire [multisegment]<pw-name>[ttl <ttl>|
ZXR10#
timeout <timeout>| source {<source-ipv4-address>|<source-ipv6-ad
dress>}|[{ddmap|dsmap}]]
master : specifies that the master LSP sends LSP ping packets.
slave : specifies that the slave LSP sends LSP ping packets.
SJ-20140504150128-007|2014-05-10 (R1.0)
Chapter 15 Network Layer Detection
15-23
ZTE Proprietary and Confidential
Function
Enables the IPv4 LDP LSP trace
function.
Enables the RSVP LSP trace
function.
Enables the PWE3 LSP trace
function.