Network Connectivity - What is dahdi_maint, and how do I use it?

dahdi_maint is a utility for diagnosing problems with T1/E1 adapters (e.g. TE121, TE122, TE207, TE420, etc.).  It is primarily used by Sangoma CTS Technical Support to diagnose problems with a PRI connection.  It allows the technician to loop the card in software.  There are three basic loopback types:  network line, network payload, and localhost.

The network line loopback configures the specified span at the physical line layer.  This is useful for the PRI provider to test the network as connected to the Sangoma adapter.  Since this is a line loopback, the frames do not pass through the framing and encoding chip on the adapter.  This type of loopback should be functionally equivalent to placing a physical loopback connector on the PRI line coming from the provider.  To enable the network line loopback on span 1, issue the following command in the Linux shell:

The network payload loopback is similar to the network line loopback, except frames will pass through the framing and encoding chip before being looped back to the far end.  This requires that the card be configured properly in '/etc/dahdi/system.conf' and should allow the provider to determine whether the PRI adapter is functioning correctly.  To enable the network payload loopback on span 3, issue the following command in the Linux shell:

The final type of loopback supported is the localhost loopback.  It is functionally equivalent to connecting a physical loopback connector directly to the span in question. With proper testing configuration of the card this allows a technician to perform a pattern loopback test to confirm proper functioning of the card.  To enable the localhost loopback on span 2, issue the following command in the Linux shell:

Note that for all of the above commands, a technician will need to initiate a test (e.g. the provider's loop test for the network loopback types, or a pattern loopback test [patlooptest] in the localhost type) after setting up the loopback mode.  To cancel the loopback on span 4, issue the following command in the Linux shell:

The above command will return span 4 to normal operation.  Note that all loopback settings can be cleared by removing and reloading the DAHDI drivers.  There are some other options to dahdi_maint (see the output of "dahdi_maint" with no options), including inserting specific error types on a span, resetting error counters on a given span, and viewing the error counters for a given span.  Inserting a specific error (with the "--insert" option) is useful to test whether the error counters are functioning correctly.  The "--reset" is useful for resetting all error counters for a particular span.  Finally, executing "dahdi_maint --span 1" with no other options will display all of the current error counters for span 1.  The counter acronyms are as follows:

• FEC = Frame Error Counter

• CEC = CRC4 Error Counter

• CVC = Code Violation Counter

• EBC = Ebit Counter (E1 only, remote end seeing errors)

• BEC = PRBS Bit error counter (Pseudo random bit sequence, currently nonfunctional)

To view more help and information about the dahdi_maint utility use the following command: