Technical data

Troubleshooting Techniques and Tools
1.2 Isolating Problems
Table 1–1 (Cont.) Diagnostic Tools
Diagnostic Tool Function
TCPTRACE Traces packets going in and out of the system. To run the trace
utility, enter the DCL command TCPTRACE.
traceroute Displays the route of an IP packet sent from the local host to a
remote host.
To enter a command at the system prompt, first run the
SYS$STARTUP:TCPIP$DEFINE_COMMANDS.COM command procedure.
This procedure defines each tool as a foreign command.
See Appendix A for complete reference information about these diagnostic tools.
1.2.1 Testing Connectivity Between Network Hosts
Use the ping command to test whether you can reach a remote host from your
local system. The ping command sends an Internet Control Message Protocol
(ICMP) echo request to the specified host name or host address. When received
by a host, an ICMP reply is returned to the requester.
When using the
ping command to isolate a problem, you should first test the
localhost to verify that the system can communicate with itself. For example:
TCPIP> ping localhost
PING LOCALHOST (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=1 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0 ms
----LOCALHOST PING Statistics----
4 packets transmitted, 4 packets received, 0% packet loss
round-trip (ms) min/avg/max = 0/0/1 ms
TCPIP>
TCPIP> ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=1 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0 ms
----127.0.0.1 PING Statistics----
4 packets transmitted, 4 packets received, 0% packet loss
round-trip (ms) min/avg/max = 0/0/1 ms
The output from this ping command shows that the system is able to send a
message down and then back up the protocol stack through the loopback address.
The host address 127.0.0.1 and its associated host name, localhost , are the
loopback address of the local host. This address was devised so that software
could use common code to address local processes as well as remote processes.
If the command output shows that it received a message for every message it
transmitted, then you can be sure that the network software is up and running
and that your system should able to communicate with remote systems.
If you do not receive output similar to that shown in the example, then one of the
following conditions may exist:
• TCP/IP Services may not be running.
Troubleshooting Techniques and Tools 1–3