# Tracing Paths Through the MPLS User Plane

#### Purpose

To trace paths through the MPLS user plane.

#### Action

To trace the path that packets follow enroute to the destination IP address 10.90.101.9:

    host1:edge1#traceroute 10.90.101.9
    Tracing route to 10.90.101.9, TTL = 32, timeout = 2 sec.
    (Press ^c to stop.)
    1  3ms  2ms  2ms       10.90.101.4    mplsLabel1=4009
    mplsExpBits1=0
    2  2ms  2ms  2ms       10.90.101.7    mplsLabel1=7004
    mplsExpBits1=0
    3  2ms  2ms  2ms       10.90.101.9

ICMP extensions enable LSRs to append MPLS header information (the label stack) to ICMP destination unreachable and time exceeded messages. This sample output shows the label and EXP bits used to switch the ICMP packets.

#### Related Documentation

- For more information about using the traceroute command, see Reachability Commands in the JunosE IP, IPv6, and IGP Configuration Guide,
- traceroute