call connect message
  • 0x0F indicates a connect acknowledgment (ack) message
    • The debug isdn q931 command is useful for observing call setup exchanges for both outgoing and incoming calls. The debug dialer [events | packets] command is useful for troubleshooting DDR connectivity. The debug dialer events command sends a message to the console indicating when a DDR link has connected and what traffic caused it to connect. If a router is not configured correctly for DDR, then the output of the command will usually indicate the source of the problem. If there is no debug output, then the router is not aware of any interesting traffic. An incorrectly configured dialer or access list may be the cause. Not all DDR problems result in an interface failing to dial. Routing protocols can cause an interface to continuously dial, even if there is no user data to send. An interface that is constantly going up and down is said to be flapping. The debug dialer packet command sends a message to the console every time a packet is sent out a DDR interface. Use this debug command to see exactly what traffic is responsible for a flapping DDR interface. If a router is not connecting when it should, then it is possible that an ISDN problem is the cause, as opposed to a DDR problem. The remote router may be incorrectly configured, or there could be a problem with the ISDN carrier network. Use the isdn call interface command to force the local router to attempt to dial into the remote router. If the routers cannot communicate using this command, then the lack of connectivity is an ISDN problem, not a DDR problem. However, if the routers can communicate, then both the toll network and the ISDN configurations on the routers are working properly. In this case, the problem is most likely an error in the DDR configuration on either router. In some cases it is useful to reset the connection between the router and the local ISDN switch. The clear interface bri command clears currently established connections on the interface and resets the interface with the ISDN switch. This command forces the router to renegotiate its SPIDs with the ISDN switch, and is sometimes necessary after making changes to the isdn spid1 and isdn spid2 commands on an interface. Lab Activity e-Lab Activity: isdn spid In this activity, the student will demonstrate how to use the isdn spid command to define at the router the service profiles identifier number that was assigned by the ISDN service provided for the B1 channel. Web Links Tech Notes http://www.cisco.com/en/US/tech/ tk801/tk133/ tech_tech_notes_ ist.html
    Content Summary ISDN refers to a set of communication protocols proposed by telephone companies to permit telephone networks to carry integrated voice, video, and data services. ISDN permits communication over high-quality, high-speed, digital communication channels. DDR is used in order to save the costs of a dedicated WAN line for organizations and companies that do not need a permanent connection. It can also be used as a backup by organizations that use the dedicated line for critical applications. An understanding of the following key points should have been achieved: