Looking For PRI Card With Automatic Fail Over

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Asterisk Users 8 Comments

I have a customer where we are putting an Asterisk PBX in front of a legacy (non-VoIP) PBX. One of the requirements it that the Asterisk PBX have 2 PRI ports (one towards the legacy PBX and one towards the carrier) with the ability to go to pass through should the Asterisk PBX (software or hardware level) fail.

I did not see this feature in the Digium, Sangoma, Allo, or OpenVox cards.

Does anyone know of a card that will do this? I know that Digium has an external box (the r850) that does something similar for 2 PBXs making them high availability, but in this case I only have the 1 Asterisk box acting as a gateway and passing some calls out over SIP and IAX2.

Any suggestions would be appreciated.

8 thoughts on - Looking For PRI Card With Automatic Fail Over

  • There was a product called something like red box or similar that I saw around 5 years ago. Probably not entirely helpful but maybe Google will help.

    Kind regards,


  • Hi there,

    Using Sangoma Vega400 gateway you’ll have what is called resilliency which is exactly what you are looking for.


  • Use a 4-pole change-over relay to switch the PRI connection either to the Asterisk box if it gets some sort of “heartbeat” signal from the computer
    (say, toggling one of the lines of a printer port, if the motherboard still has one), or the old PABX?

    You might have to do some mean, down and dirty low-level programming, to embed your heartbeat-generating code in Asterisk’s idle loop; but the Source Code is out there, if you fancy the challenge …..

  • Building on the answer above, have a look at ESL labs – who make such a relay that can bypass the PRI to the Asterisk server. As well, have a look at HAAst (www.telium.ca) which can monitor Asterisk and then control the ESL relay to bypass Asterisk in case of failure.


    P.S. My opinions do not necessarily reflect those of my employer. As I
    am employed by Telium you can bet that me opinions are biased!

  • Responding to Matt Riddell, M Shokuie, A J Stiles, and Telium Support (all below)

    Thanks for the suggestions, but a separate gateway is a problem in the design as the configuration is basically:

    Carrier — PRI — Asterisk (with failover) —- Legacy PBX
    – SIP / IAX2 — our service or remote office

    As this is already acting as a gateway adding another box to the mix seems a bit over kill (unless I can embed it and the asterisk PBX into a 2 U
    pizza box). But since most gateways are designed to be used for fail over servers / PBXs not lines I am not sure that this would benefit us.

    So far I have found 1 company that seems to have a gateway card and that is the beroNet PCI / PCIe Gateway Cards which they say has the card level failover. I will update the list should this meet the use case. Eric


  • If you place an ESL PRI A/B switch on either side of the Asterisk server you can easily bypass the Asterisk server, or place it inline with the PRI link.

    You can also chose to TAP the lines as noted above, but you have to ensure that both PRI cards don’t go live at once…(if I understand that product correctly).