ISDNguard Watchdog Advice

Hi All

I’m currently investigating a automatic failover unit for our ISDN between our two servers. I’ve spotted Junghanns ISDNguard which looks ideal.

I’ve not purchased the unit but looking at the manual it uses a watchdog ticker to keep the line up. If asterisk stops the ticker stops so it falls over to the secondary, ideal for us as others I’ve found rely on ping or sync from the E1 which would all stay up if Asterisk crashed for some reason.

What I’m not sure about is how the ticker integrates with Asterisk.

It says in the below manual to add a few lines to \etc\asterisk\watchdog.conf however I don’t have this conf file. If I created it would Asterisk automatically parse it or do I need to add reference to it somewhere?

If you have Sangoma T1/E1 cards (perhaps others also) you can save several hundred dollars and parallel two cards quite safely because if dahdi and/or wanrouter is stopped on one server, the TX lines will then be in a high impedance state I use a few hundred ohm resistors in each signal line after the split as an added precaution. the TDM line will drop briefly on changeover but so would your proposed solution.

Hi dicko

Sounds very interesting. I’ve looked further into the watchdog thing and along with the Openvox unit requires an Asterisk module to be loaded which means re-compiling. That’s put a complete stop to both units as I’m not even going down that road.

As for your suggestion, My primary and secondary are in separate buildings. Both have Sangoma A101DE cards and the secondary is fed via an E1 to fibre unit (at each end) which I dont think would make any difference to your suggestion.

Are you able to give any more details on how to achieve your cable setup, I have a rough idea on what you’re saying but would like a little more info to try it out. Just hoping I don’t blow stuff up if i do it wrong.


I don’t think my solution would work for you as the RJ48 to E1 extender interface would always load 120 ohms on the TX side. I personally would look for a redfone (unfortunately now defunct but incredibly sturdy) on ebay if you have a layer 2 network between both machines, failing that a E1 to SIP gateway and rely on your layer 3 network.