Filter
Top Products
Monitoring and Testing
4-19
3166-A2-GB20-10
November 1998
Local Loopback Tests
The Local Loopback tests enable you to conduct circuit testing and fault isolation
for the digital line. The supported local loopback tests are:
H Line Loopback (LLB)
H Payload Loopback (PLB)
H Repeater Loopback (RLB)
H Data Channel Loopback (DCLB)
H Data Terminal Loopback (DTLB)
The Line Loopback command can be activated and deactivated in response to
commands received over the network interface. The Network Interface
configuration option NET LLB controls whether the DSU/CSU responds to the
commands transmitted on the network interface to initiate LLBs (see Appendix C,
Configuration Options
).
The data port configuration option NET DCLB controls whether the DSU/CSU
responds to inband V.54 commands to initiate DCLB for that port (see
Appendix C,
Configuration Options
).
Local loopback tests can be aborted (Abort Command) at any time.
Local loopback tests cannot be run if send pattern or remote loopback tests are
active. In most cases local loopbacks cannot run with each other. Table 4-7
shows valid combinations of local loopbacks.
Table 4-7. Valid Loopback Combinations
LLB PLB RLB DCLB DTLB
LLB
NO NO YES NO YES
PLB
NO NO NO NO YES
RLB
YES NO NO NO YES
DCLB
NO NO NO NO NO
DTLB
YES YES YES NO NO