3Com Switch 7750 SeriesCommand Reference Guide – System Maintenance & DebuggingChapter 2 Network Connectivity TestCommands2-4-q num-packet: Sets the number of packets to be sent every time. The nqueriesargument ranges from 0 to 65,535 and defaults to 3.-w timeout: Sets the timeout time to wait for ICMP error packets. The timeout argumentranges from 0 to 65,535 and defaults to 5,000 (in milliseconds).host: IP address of the destination host or the host name of the remote system, 1 to 30characters long.clns: Connectionless network service, a suit of protocols in OSI system, including CLNP,ISIS and ESIS.-m max-TTL: Sets a maximum TTL value. The max-TTL argument ranges from 1 to 255and defaults to 30.-n num-packet: Indicates the integral number of the sent test packets. The num-packetargument ranges from 0 to 65535 and defaults to 3.-t timeout: Sets the timeout time of the tracert command. The timeout argument, inseconds, ranges from 0 to 65535 and defaults to 5.-v: Explains the error if the response packet error occurs. If no error occurs, after youexecute the command, the result is the same as the command is executed without -v.nsap-address: NSAP address of the destination host.DescriptionUse the tracert command to trace the gateways the test packets passes through duringits journey from the source to the destination. This command is mainly used to checkthe network connectivity. It can help you locate the trouble spot of the network.The executing procedure of the tracert command is as follows: First, the source sendsa packet with the TTL of 1, and the first hop device returns an ICMP error messageindicating that it cannot forward this packet because of TTL timeout. Then, the sourceresends a packet with the TTL of 2, and the second hop device also returns an ICMPTTL timeout message. This procedure goes on and on until a packet gets to thedestination or the maximum TTL is reached. During the procedure, the system recordsthe source address of each ICMP TTL timeout message in order to offer the path thatthe packets pass through to the destination.If you find that the network is in trouble by using the ping command, you can use thetracert command to find where the trouble is in the network.The tracert command can output the IP addresses of all the gateways the packets passthrough to the destination. It output the string "***" if a gateway times out.Example# Trace the gateways the packets pass through during its journey to the destination withIP address 18.26.0.115.<3Com> tracert 18.26.0.115
