We have some physical servers that we cannot virtualise because they are connected to analog modems for alert paging.

We need to retain this functionality, but virtualise the servers and reduce the pile of individual modems down to something that can be rackmounted in a minimal number of U.

So I guess I'm seeking a stack something like this:

  • Rackmount bank of 8-16 modems
  • Network connectivity from the modem bank onto the network
  • Some kind of client software on the VMs that allow them to create a modem COM port, via the IP connection

I'm already familiar with a partial solution - MOXA make an IP-connected serial server that can connect to a bunch of modems. This works in exactly the manner we need, but it doesn't go as far as integrating the modems - So we still have a bunch of them sat on rack shelves.

Can anyone point me in the right direction on this?

Edit: I'm thinking I can probably get closest to what I'm after by stacking one of these with one of these. I was hoping there would be an integrated, single-unit solution but maybe not.


I'm not sure if there's a client, but it sounds like you should be able to use reverse telnet to a Cisco AS5300. The AS5300 takes a PRI (T1 with ISDN framing, so 24 phone lines worth) and should support dial-out (I think), in a single rack space.

  • Ah, this sounds like something closer to my requirements. Are there any options here for presenting it to the LAN-connected servers as a modem? Some of the apps we use are expecting a standard hayes-compatible sitting on a COM port. Jul 10 '10 at 13:07
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    For Windows, there is (used to be?) DialOut/EZ, and there's Lantronix COM Port Redirector For *NIX, 'socat' sounds like it should work.
    – techieb0y
    Jul 11 '10 at 3:55

Check out the Digi Serial servers. We use one to go the opposite way (TS 8/16) - hook up 1 modem as an emergency dial-in to our networking stack so we can still get to it in an emergency.

If i remember the docs right you and absolutely go the opposite way, hook a bunch of modems up and setup COM devices that talk over ehternet using their driver.

  • They look like they accomplish as much as the MOXA - Serial-to-ethernet, but not end-to-end PSTN-to-ethernet (which is what I'm after. Basically I'm hoping for a device that can concentrate down the 15 modems we have rattling around, into a few rackmount units. Jul 9 '10 at 6:42

Why bother with paging anymore? You can accomplish the same thing with SMS.


  • We dual deliver via paging and SMS. Our experience has been that the pager network is generally more resiliant, especially during wider outages to mobile networks. Also, coverage is more complete our on-call admins that still want to head out in the country over the weekend. Jul 9 '10 at 6:39
  • @Chris Thorpe: +1 for using pager alerts as a backup to your SMS alerts. I also use pager alerts via modem and POTS line in case the network and\or email system is down, rendering my email alerting system useless.
    – joeqwerty
    Jul 9 '10 at 13:33

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