[asterisk-users] High Availability with Asterisk

Hans Witvliet asterisk at a-domani.nl
Sun Mar 9 15:16:10 CDT 2014

On Sat, 2014-03-08 at 20:27 +0000, adamk at 3a.hu wrote:
> My approach (in theory only, so please correct me if I'm wrong) would be 
> to run asterisk on multiple boxes (one each).  A dedicated monitoring 
> box (nagios?  custom scripts?) would perform frequent checks against the 
> boxes (one of my previous projects one asterisk was using call files to 
> demonstrate its health to another one).
> If a box fails, I would simply redirect/reroute its traffic to another 
> one, using network solutions.  Such as shutting down the production 
> interface of a suspectedly failed asterisk box, having an idle one pick 
> up its IP address, or using load balancing / routing / NAT to redirect 
> the client's traffic to a standby box.
> My approach is based on the experience that linux based HA tools are 
> often not free, or don't scale well, or engineered to circumvent an 
> error in a slower manner (eg. booting a second VM takes too much time). 
>   However in the network world, there are well known protocols that were 
> designed to take over in a matter of miliseconds.
> I do understand that this would not provide 'session' data, so failing 
> over to a different box would mean the need to re-register, could cause 
> calls to drop etc.  This might be unacceptable for you.  As I said in 
> the beginning, I haven't been building such systems, in my experience a 
> dropped call is not that big of a deal, if it happens because the 
> network cuts over to a different box.  This could be handled with a pair 
> of frontend load balancers, where the number of asterisk boxes can be 
> transparent.
> hope this helps
> adam

Hi Adam,

Don't confuse "high availability" with "load balancing", as these two
are not related. These two have totally different objectives and are
achieved in different ways.
Either/both of them can very well be achieved with opensource tools.

Even with commercial software is maintaining call when a intermediate
PABX breaks down nearly impossible

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