atcomsystems.ca/forum Forums TDM Business Telephone Systems Toshiba Telephones & Systems IP Phones random disconnection from IPU

I'm happy to know that I'm not alone in this issue, frankly I was wondering why I hadn't heard more people complaining about this problem! The Toshiba systems are old now, but still in wide use.

The SonicWall that you have is likely for your network in general, this solution requires a dedicated device (though who knows if there is another way using other devices). The ZyXEL ZyWall USG 20 looks to be around $200 on Amazon at the moment, so it didn't seem worth investigating since this was the "known" solution.

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There should be a way to use Sonicwall, but I have had several IT fail to get it to work. A 5 port switch ends up being the easy solution.

SonicWalls are one of the harder firewalls to deal with when it comes to VOIP. I have several cheat sheets I can send if interested, it gotten to the point that if the IT person or company has never done VOIP we will go around them with public IP's.

However we have chased issues with everything being public and had these issues as well. In those cases it is always the carrier blocking something or in our case the Comcast modems blocking or having a setting activated that should not be.

Make sure you have good up to date firmware on the IP cards and the correct phone firmware. I have seen a bunch of LIPU's that will work flawless with older firmware on the 5xxx series phones but crap out with the latest and greatest.

I think in almost every case, we end up using a direct connection to the MIPU. I have had some IT try to say that they can get it to work with NAT. I say to them, well let Toshiba engineers know of your miracle solution because so far this has never worked with the MIPU. In the case of the ZyXel, Toshiba actually took the time to make a step-by-step example of how to firewall the MIPU using this specific router. Years ago in Toshia's class, we tried to do the same thing with a SonicWall router, but we could not get this to work in the lab environment. I am sure that there is a solution with other router models. I no longer have the time, or desire to figure out Toshiba PBX solutions in my office lab.

Sonicwall does work well with SIP trunks to Toshiba behind a NAT using ALG (SIP transformations). I have several SIP trunks working through Sonicwall. The Toshiba IP phones do not use SIP. That is why you won't get them to work through NAT.