I'm quite new to SIP and VoIP telephony in general and I have a (supposedly) simple question to spare.
A customer of mines owns a classic PBX with a spare extention line (FXS) which she would like to connect to a remote office.
I thought this was easy to implement. Looking for a very simple solution, I had the impression that a Cisco SPA 400 Internet Telephony Gateway plus a Cisco SPA 502G IP Phone would do the trick and would even allow for further IP Phones (which are really not needed right now).
Then, I started having a lot of doubts. First of all, every Cisco reference about the SPA 400 seems always referring to the SPA 9000 too, to the point that I'm going to think that a SPA 400 and a SPA 502G wouldn't work without a SPA 9000. Am I right?
What I basically I'm looking for, is a very simple and inexpensive VoIP solution which would allow the remote user to be remotely, 1-to-1 connected to a specific PBX extention line. Basically, I would like that when the remote user picks the handset, he/she would ear the PBX call tone (or, of course, pick the outstanding call in that extention). So, in case the SPA 400 + SPA502G mix isn't the right way to do this, can you head me to the right solution?
Of course, the remote office's LAN will be connected to the main one through a simple VPN. QOS and the like will be activated in the routers in order to give enough bw to this app.
SPA400 is not the right product in principle. You better go for either SPA3102+SPA2102 (for one phone only) or for SPA8800s (for multiple ports). The operation is as follows. Connect a SPA3102 or SPA8800 FXO port to the PBX extension line. Then on the remote site place the other ATA (SPA2102 or another SPA8800).
You need to setup peer to peer SIP trunks between the gateways (there is a similar post on this community - use search function), one important aspect is that you need static public IP addresses in order to have these devices to talk each other without a proxy.