How does ISDN backup work

[Kevin Melton]

I am consulting at a company that uses Frame Relay to connect to alot of its WAN sites. They have a backup system that uses ISDN to dial if the Frame ever fails.

I was looking at the ISDN router today as well as one of the routers at one of the WAN sites, and it is not apparent how the ISDN is triggered when the Frame Fails.

What should I be looking for here? I am going to post a config here with the dial string altered so that someone whom has experience with this may be able to help.

Thanks

Kevin

[Giuseppe Larosa · Accepted solution]

Hello Kevin,

>> dialer watch-list 1 ip 192.168.3.0 255.255.255.0

the dialer watch list feature is used:

it monitors the presence in the routing table of one or more IP prefixes.

if the prefixes are missing it dials to HQ.

this is handy to implement dial backup over multiple routers: that is primary link and backup link are on different routers.

Hope to help

Giuseppe

[Kevin Melton]

Youre answer makes perfect sense. That is a slick feature. Thanks Guiseppe.

[Kevin Melton]

Guiseppe

Would you know what the following command is used for called chat script?

virtual-profile virtual-template 1

async-bootp dns-server 192.168.1.95 192.168.1.53

async-bootp nbns-server 192.168.1.95 192.168.1.53

isdn switch-type primary-ni

isdn voice-call-failure 0

chat-script generic ABORT BUSY ABORT NO ## AT OK ATDT\T TIMEOUT 30 CONNECT

chat-script Dialout ABORT ERROR ABORT BUSY "" "AT" OK "ATDT \T" TIMEOUT 60 CONNECT \c

Thanks

Kevin

[Giuseppe Larosa]

Hello Kevin,

this is true dialup stuff.

these commands are an ordered list of AT commands to be given to a modem connected to a line.

they include events like ABORT, BUSY and commands to sent to the modem like ATDT.

imagine that it is like a telnet session to the modem and that you receive messages and send commands

Hope to help

Giuseppe