The last implementation method specific reply code received.
The Alcatel-Lucent SROS OAM Trace Route is usually implemented by
transmitting a series of probe packets with increasing time-to-live
values. A probe packet is a UDP datagram encapsulated into an
IP packet. Each hop in a path to the target (destination) host
rejects the probe packets (probe's TTL too small, ICMP reply) until
either the maximum TTL is exceeded or the target host is
received. For icmpTraceRoute, both icmp packet type and code
are included.