Справочник Пользователя для 3com WX4400 3CRWX440095A

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ERVICES

To identify the next hop, traceroute again sends a UDP packet, but this 
time with a TTL value of 2. The first router decrements the TTL field by 1 
and sends the datagram to the next router. The second router sees a TTL 
value of 1, discards the datagram, and returns the Time Exceeded 
message to the source. This process continues until the TTL is 
incremented to a value large enough for the datagram to reach the 
destination host (or until the maximum TTL is reached).

To determine when a datagram has reached its destination, traceroute 
sets the UDP destination port in the datagram to a very large value, one 
that the destination host is unlikely to be using. In addition, when a host 
receives a datagram with an unrecognized port number, it sends an ICMP 
Port Unreachable error to the source. This message indicates to the 
traceroute facility that it has reached the destination. 

To trace a route to a destination subnet, use the following command:

traceroute host [dnf] [no-dns] [port port-num] [queries num] 
[size size] [ttl hops] [wait ms]

To trace the route to host server1, type the following command:

WX1200# traceroute server1
traceroute to server1.example.com (192.168.22.7), 30 hops max, 38 byte packets
1 engineering-1.example.com (192.168.192.206) 2 ms 1 ms 1 ms
2 engineering-2.example.com (192.168.196.204) 2 ms 3 ms 2 ms
3 gateway_a.example.com (192.168.1.201) 6 ms 3 ms 3 ms
4 server1.example.com (192.168.22.7) 3 ms * 2 ms

In this example, server1 is four hops away. The hops are listed in order, 
beginning with the hop that is closest to the WX switch and ending with 
the route’s destination. (For information about the command options, see 
the 

.)