Asterisk and redundancy

Dear members,

It’s my first post and I am very pleased with the knowledge on this forum, and am happy to be a part of this.

I have an asterisk system running now for 2 years that is not working as expected. All sort of little problems are making my life difficult. Sometimes the server stops working, sometimes the setting somewhere changes from PTP to PTMP and visa versa for the ISDN lines etc. etc. We want more contingency.

Specs pf the existing connections
There are 3 ISDN lines and 2 pot lines connected to this asterisk. There are 70 VOIP extension on the LAN and 10 on the WAN. We have 20 Utstar F1000 handsets that have to work in the house as well as in the rest of the world without having to reconfigure them.

To solve the contingency problem, we are going to:
add an extra asterisk server parallel to the existing one for server fail over.
add a VOIP service provider to be a fail over for the ISDN lines.

To solve the f1000 problem i would like to place both the servers direct on Internet with a fixed WAN IP address for each.
Then I would place the existing Cisco pix (no dmz) firewall parallel to the 2 servers with another fixed WAN IP address to serve a LAN dedicated to VIOP.

In this case all the VOIP phones will be configured with the WAN IP address of an asterisk server.

Is this setup ok?

How is the physical connection to the Internet? Do I place a switch between the SDSL router and the 2 asterisk’s and the pix firewall?

Now only one server will be active and the other one will be in standby mode. How do i do automatic switchover from one asterisk to the others asterisk without to reconfigure the IP address in the VOIP phones?

Is there something els that i can do to have good fail over?

Thank you all,


I’m no expert in this but google is your friend. Search of “Asterisk HA” turns up many useful pages, including … +Solutions.

If active-standby is your preferred configuration, don’t configure your phones with IP address; use domain name instead. Then you simply reconfigure your DNS to switch over.

DNS propagation may take some time. So a better solution would be to reconfigure network interface - don’t have to use domain name in this case. (I assume that you’ll have a second private interface to start with - or a console interface.) Even better, don’t use two public IP addresses. Use a NAT so you only have to reconfigure the router.

It seems that you are only concerned about IP failover - there are plenty of other ways to do it. I’m curious to know how do you fail over ISDN bank in case of server failure.