2
Using Loopback Tests
Loopback tests send test messages over a particular communications path
and then loop them back to the originating node. This operation checks the
communications links and helps you isolate the cause of any faults. If the
originating node successfully receives the test messages, you can assume all
components along the test path are working properly. Tests along different
paths help you isolate problems in specific areas of a DECnet SNA network.
Loopback tests for the Gateway-ST fall into two main categories:
•
DECnet NCP loopback tests. These tests check the communications
software and hardware from the DECnet Management node to the
Gateway-ST node. If you have been receiving DECnet error messages, you
should run these tests. The tests are described in Section 2.1.
•
SNANCP loopback tests. These tests check the communications
hardware from the Gateway-ST to the modem at the IBM site. You should
run SNANCP loopback tests in either of the following cases:
If you have been receiving SNANCP error messages or SNA-related
event messages.
If the SNANCP command SHOW LINE line-id COUNTERS indicates
excessive error counters on the line.
The SNANCP loopback tests are described in Section 2.2. For more details
on the SNANCP commands, refer to the
DECnet SNA Gateway-CT and ST Management book.
In addition to NCP and SNANCP loopback tests, DEC MicroServer loopback
tests are available. Section 2.3 describes the DEC MicroServer loopback tests.
Use these tests when you cannot use the test facilities offered by the DECnet
SNA Gateway for Synchronous Transport software.
Using Loopback Tests 2–1
