Simple Analysis of six common ISDN troubleshooting methods

This is one of the most common routing faults caused by ISDN routing faults. So I have studied the classification and solution of ISDN routing faults. Here I will share with you my hope to help you. ISDN is the abbreviation of Integrated Services Digital Network. It evolved from Integrated telephone Digital Network IDN to provide end-to-end Digital connections, supports a wide range of businesses, including voice and non-voice services ).

ISDN provides users with a limited set of standard multi-purpose user-network interface UNI), The ITU-T I .412 recommendations for the user-network interface for the two interface structure: basic interface BRI) and a group rate interface PRI), BRI bandwidth is 2B + D, PRI bandwidth is 30B + D or 23B + D. The channel is a user channel used to transmit voice, data, and other user information. The transmission rate is 64 Kbps. The channel is a control channel that transmits public channel signals, these signaling rules are used to control calls on the B channel of the same interface. D channel speed is 64 KbpsPRI) or 16 KbpsBRI ). ITU-T Q.921 is the data link layer protocol of D channel. It defines the rules for user to switch information between layer 2nd entities through D channel on the network interface, and supports the access of layer 3rd entities. ITU-T Q.931 is the network layer protocol of D channel, which provides a method to establish, maintain, and connect to the final network between communication application entities.

ISDN route fault: physical fault of the ISDN Interface

(1) PRI Interface
Use the display controller e1 command to check whether the physical connection of this interface is correct. If the cE1/PRI interface is DOWN, it indicates that the physical connection is incorrect. It may be caused by interface disconnection or coaxial cable backend. You need to tighten the connector or adjust the coaxial cable connection. If you have confirmed that the physical connection to the interface is correct, but still cannot enter the UP state, check the physical frame format encapsulation at both ends of the cable, Quidway26/36 series routers by default use the NO-CRC4 frame format validation. The cE1/PRI interface can enter the UP State normally only when the frame format check configurations at both ends of the cable are consistent.

(2) BRI Interface
When no call is made, its interface is always deactivated. When the vro is powered on, the display interfaces bri command can be used to query whether the physical status of the interface is UP and the Protocol status is spoofing. Therefore, the physical status of the BRI interface cannot be determined if it is normal when no call is made.

ISDN route fault: ISDN interface link fault

When the physical status of the PRI interface is normal or the BRI interface is used for call, if the debug isdn q921 command is used to display only SABME frames, but not the RR frames sent and received, the Q.921 link fails to be established. If Q.921 fails to be established, we recommend that you describe the communication parameters and procedures between Asymmetric devices, that is, either end of the cable must be the user side and the other end must be the network side. Quidway26/36 series routers currently only support the user side. Therefore, the vswitch connected to the vro must be configured as the network side. Otherwise, the chain cannot be established successfully.

ISDN route fault: physical fault of Modem

The physical failure of the Modem may be caused by the following reasons: the Modem is connected to the router's synchronous or asynchronous interface through the V.24 coaxial cable, if "OK" is not displayed after the debug modem at command is used, it indicates that the Modem is abnormal. You can turn off the power and reset the Modem again. If you can see "OK", the caller's Modem is always dialing, but there is no "choppy" sound in the receiver), you need to check whether the Automatic Answer attribute of the Modem is correct. For some Modem attributes, the router should use the undo modem auto-answer command to cancel the automatic response. If the Modem attribute is not an automatic response, the router needs to use the modem auto-answer command to configure the automatic response attribute. The Modem dialing success rate is related to both the Modem quality and the line quality.

If you cannot confirm whether the Modem is an automatic response, you can use a Super Terminal to connect to the Modem and use the AT command at & v to view the response. If ats0 = 1 indicates automatic response, and ats0 = 0 indicates non-automatic response. If you need to set the automatic response attribute of the Modem on the vromodem, use the ats0 = 0 command to set the non-automatic response, or use the ats0 = 1 command to set the automatic response, use the at & w command to save the configuration. If you have confirmed that the Modem is normal and there is always a busy tone in the call, it means that the called end is busy and the peer line may be in use; or the two ends are simultaneously trying to call the peer end, resulting in a call conflict. When the call line is in use, you can wait for the Peer to stop and try again. If a call conflict occurs, you can use the dialer timer enable command to set the call interval between the two ends to different values to avoid the next call conflict.

ISDN route failure: Same/asynchronous Modem dialing configuration problems

First, determine whether synchronous dialing or asynchronous dialing is used. For synchronous dialing, the interface must be a synchronous dialing interface; for asynchronous dialing, if the same/asynchronous interface is used, that is, the Serial interface ), you must first use the physical-mode asynchronous command to set this interface to an asynchronous port, and use the command modem to set the Modem dialing attribute. For an asynchronous interface, that is, the Async interface ), directly use the modem command to set the Modem dialing property.

ISDN route failure: Initiate dialing

The IP address or IPX route of the dial-up interface fails. If the debug ip packet command is used to turn on the debug switch and a message indicating a route failure is displayed, run the display ip route command to check whether the route is correct, use display current-configuration to view the configuration of the dialing interface and check whether the IP address or IPX address on the dialing interface is correctly configured.

ISDN route failure: the dial-up interface is not enabled

Run the debug dialer event command to enable the dial-up debugging switch. If the "DCC: DCC must be Configured on the interface" prompt is displayed, run the "display current-configuration" command to view the dialing interface configuration, for Round Robin DCC, the dialer enable-circular command must be used to enable DCC. For shared DCC dialing interfaces, the dialer user command and dialer bundle command must be used to enable DCC.