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SPID error


When the main frame goes down and the backup ISDN tries to comeup we are getting "invalid spid" error message.. The carrier confirmed that the SPID number we are using on the router is correct but we still getting the same error.. Any Idea what could be the reason?

The carrier told us to check the SPID number on the modem? Which modem?

Thanks in advance



Do you have the SPID configured in your router (assuming you have an internal ISDN interface)? Depending on where in the world you are, this may need to be done.


I believe you are on the North America area and specifically requires SPID for ISDN configuration on your router.

Maybe need to check the SPID number again and must take note some requires you to append/prepend a couple of digits on the actual SPIDs.


Rising star
Rising star

Hi ,

Some service providers use service profile identifiers (SPIDs) to define the services subscribed to by the Integrated Services Digital Network (ISDN) device that is accessing the ISDN service provider. The service provider assigns the ISDN device one or more SPIDs when you first subscribe to the service. If you are using a service provider that requires SPIDs, your ISDN device cannot place or receive calls until it sends a valid assigned SPID to the service provider when accessing the switch to initialize the connection.

Currently, only the DMS-100 and NI-1 switch types require SPIDs. The AT&T 5ESS switch type may support a SPID, but you should contact your provider for information on what the SPID must be configured as. Remember that SPIDs are only required in North America and are configured only if required by your telco/provider.

Use the show isdn status command to check if the SPID is valid. For more information on using the show isdn status command, refer to Using the show isdn status Command for BRI Troubleshooting.

SPID Format

A SPID is usually a ten-digit telephone number with some optional numbers. However, service providers may use different numbering schemes. For the DMS-100 and NI-1 switch types, two SPIDs are assigned, one for each B-channel. For more information on the SPID format, refer to Known SPID Formats .

The format for the SPID configuration command is isdn spid1 spid-number [ldn] . For example:

isdn spid1 51255544440101 5554444

Three Digit Area Code

Seven Digit Telephone Number

Additional Digits (Optional)

Local Directory Number (LDN) (Optional)





In this case, 51255544440101 is the SPID number, and the following seven digit number (5554444) is the optional LDN. Although the LDN is optional, it must be configured if it is required by the telco.

The LDN is not necessary for establishing outgoing connections, but it must be specified if you want to receive incoming calls on the B-channel 2. The LDN is required only when two SPIDs are configured (for example, when connecting to a DMS-100 or NI1 switch). Each SPID is associated with a LDN. Configuring the LDN causes incoming calls to the second B-channel to be answered properly. If the LDN is not configured, incoming calls to the B-channel 2 will fail.

Common SPID Configuration Problems

Use the show running-config command to check the SPID configuration under the Basic Rate Interface (BRI). Reference the SPID format above and verify the following points in the SPID configuration:

The area code in the SPID should not be preceded by a 1.

The LDN should not include the area code.

The additional digits following the area code and telephone number are configured correctly as prescribed by the telco. In the example above, these digits are 0101.

HTH & Thx


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