Using VoIP at a remote location

[exeye]

I'm new to all this and can't figure something out. Any guidance will be greatly appreciated.

What I'm trying to do is to connect to a small office LAN from a home computer. The catch is that the home's LAN has a VoIP phone on it that needs to be part of the small office VoIP network. In other words, the home computer needs to bridge at least some home-LAN traffic to/from the office LAN.

It seems to me that this could be done by running SoftEther Server on a computer on the office LAN, running SoftEther Client on the home computer, and adding a couple of routes to the home computer's routing table. But I don't know how to do this, or even whether it would be a good idea.

Alternatively I could put SoftEther Server on an office computer and SoftEther Bridge on the home computer, with the office network being 192.168.1.* and the home network being 192.168.2.* or something like that. This is where I get lost. Would it be preferable to have both networks be 192.168.1.* but with non-overlapping addresses? That would lead to both networks having gateways of 192.168.1.1, which I don't think would work. But if I use different network segments, what tells VoIP traffic to get routed to the other network segment instead of to the Internet? Do I need a netmask of 255.255.0.0 on the home network? What about there being two DHCP servers on the bridged network?

I'm trying to do this using a single physical network adapter on both machines. The networks are very fast and there won't be a lot of traffic. If necessary I can add a second network adapter to either or both machines.

In any case what I want to accomplish is pretty simple, and there should be a simple way to set it up. And any of the solutions I have come up with lead me into what seems to me to be dangerous territory. So I very badly need to be pointed in the right direction.

Thank you.

-jimc

[dajhorn]

The limiting factor here is probably the VOIP phone because most of them can only route through the default gateway. Try something like this:

1. Office LAN:
1a. IPv4 range: 192.168.1.0/24
1b. Default gateway: 192.168.1.100
1c. DHCP address pool: 192.168.1.110 to 192.168.1.150

2. Home LAN:
2a. IPv4 range: 192.168.1.0/24 (same)
2b. Default gateway: 192.168.1.200 (different)
2c. DHCP address pool: 192.168.1.210 to 192.168.1.250 (different)

3. In the SoftEther server running on the Office LAN:
3a. Create a virtual hub and L2 bridge it into the physical ethernet interface.
3b. Create a user account for the Home LAN server in this virtual hub.

4. In the SoftEther server running on the Home LAN:
4a. Create a virtual hub and L2 bridge it into the physical ethernet interface.
4b. Create a Cascade Connection to the Office LAN server.
4c. In the Security Policy of that Cascade Connection, enable the "Filter DHCP Packets (IPv4)" policy.

The magic here is that SoftEther makes the Office LAN and the Home LAN behave like a single ethernet segment for everything except DHCP traffic. This configuration is compatible with even the worst mini-routers and CPE that are provided by AT&T/Bell/Cogeco/Cox/Rogers/Verizon et al.

This means that the VOIP phone can get a direct SIP registration at the Office LAN but still use its local Internet connection for everything else.

Remember that any IP address on a bridged ethernet interface is inaccessible to the far side of the VPN connection. The VOIP phone on the Office LAN will be unable to contact any service running on the SoftEther host at the Office LAN.

[exeye]

Many thanks for your detailed and helpful reply. I will set this up on Monday and report back on my (hoped-for) success.

-jimc