ISDN question

Unanswered Question
Jul 29th, 2007
User Badges:


I have 4 different sites which are connected with diginet lines. When these lines go down the routers are meant to automagically open the ISDN lines and dial out to connect the site.

The problem is that this has never worked before I joined the company and the people were told Cisco routers cannot do it as it doesn't work. I disagree with that I as used to work at a company where some customers had that setup and it worked perfect. Unfortunately it was too long ago and I cannot remember the commands. All I remember is the ISDN line weight must be more than the diginet line, while the diginet line is working.

So can someone please assist me with the interface configs for the isdn as well as the diginet line?

Also does anyone know of a site where I can read more about what the different cisco commands do when configuring ISDN interfaces on routers? (I have to brush up on my isdn knowledge)



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
paolo bevilacqua Sun, 07/29/2007 - 06:56
User Badges:
  • Super Gold, 25000 points or more
  • Hall of Fame,

    Founding Member

Sure it will work nicely. This is called "DDR backup". There tons of documents (perhaps too many) on CCO. The "weight" that you are referring to is the "floating static administrative distance". Then there is a part that is customized depending on what routing protocol do you use if any, and how do you want the thing to work, who does call who, etc.

Hope this helps, please rate post if it does!

Danilo Dy Sun, 07/29/2007 - 06:59
User Badges:
  • Blue, 1500 points or more


Its called ISDN Backup using Floating Static Route. The config is the same whatever is the WAN link type of the primary link.

ISDN Backup using Floating Static Route


Take note that ISDN2 has no SLA. It's good to schedule manual failover during non-production period. You can do it once a year, or once every 6 months for a specific period of time (i.e. 1 hour). To make sure that ISDN is healthy and config is working. There are some who called the ISDN numbers once a day and record that its working :). So when DR really happens, you are pretty sure that your ISDN is there for you 100%


This Discussion