1st you need to check the cable connection, please make sure that it is OK. 2nd, please check the configuration for ISDN, please look the manual for the configuration example, please check the PPP authentication configuration clearly, make sure that if you use pap, you need to configuration send pap user and password configuration, if you use chap, you need to define the chap hostname, and so on, please make sure that no other errors not related with isdn make the isdn cant up.
Q: If I use ISDN 128K line, how can I set the line speed?
A: Interface bri 1/0
PPP multilink
Q:If my isdn line can’t up, how can I do?
A: 1st, check the isdn configuration from the manual, make sure that you have set the right username and password of the isdn line, if all of these r correct, then 2nd ,please use the commands below to log the info and send to TS :
Show run
Show version
Show isdn status
Debug isdn q921
Debug isdn q931
about router reboots or hangs
Q：The router will auto reboot while it works normal, and when it starts up again, it will work well again,
A：Please use show break to log the break and send to me. And also you need to check the interface data flow and CPU usage with command: show interface and show CPU, suggest log it per hour and at least log it 5 times. And also suggest using show IP traffic to log the router’s data throughput
Q:The router will work for some time and then go to hang and never work well until reboot it manual.
A:1st need to check that you are using console line to monitor the router but not using telnet, 2nd need to check if the router was working or not, such as if there were some PCs connect to the router, check if they could do connect with others from the router or not, if it can, that means only the console line don’t work, maybe the CPU usage too high, but it is no problem. If it can’t, it means the router really hangs, so need to do the same steps as above.
About the router can't work
Q：Interface can’t come up
A：If the router can’t connect to the remote side, please check the configuration first. If it was Ethernet interface, check the IP and mask configuration is correct or not, and the link LED is light or not, make sure the UTP cable is good. If it was serial interface, make sure you had configured the same protocol and the same IP mask, and please make sure that the interface had been set the clock rate with command physical speed on the DCE end, and make sure that if you use V.28 cable, you can get a highest speed at 128Kbps and if use V.35 cable you can get 2M speed.
Q: Interface is up, but can’t ping to remote IP through the gateway ip address
A: 1st need to make sure you can ping to the gateway IP address, 2nd make sure you have configured at least one default static route point to the gateway, and make sure that if you configured more than one route, the destination IP address you want to ping will go through the right gateway IP address.
Q:Console port can’t work
A: 1st check the hyper terminal settings, the baud frequency should be 9600. 2nd, check the console cable, change another cable to try again. 3rd, change another PC to try again. 4th, if all above cant work, the console port is bad.
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ISDN problem