Voip over vpn?

Question

Asterisk

There is a task,
Given: two offices 1 and 2 remote from each other, respectively.
1 office 14 machines running windows 7, and 2 XP machines, 1 zyxel keenetic start router wired internet from Beeline provider dynamic public IP (l2tp, 80 mb/sec), 2 analog city lines each connected to 2 parallel phones.
2 office 4 machines running windows 7, the same Beeline Internet (l2tp, 80 Mb/s) is only connected using the Ubiquiti LiteBeam Wireless Bridge, 5GHz, 23dBi and the same zyxel keenetic start.
Here's what I would like to achieve:
A full-fledged internal network between two offices, each computer sees all the others in its network folder.
Employees of office 2 can make and receive calls from one of the city lines of office 1, also receive internal communication between all employees
Office 2 employee can receive a fax from one of the city lines of office 1
My guess is that the network should be organized via VPN
In office 1 for one city put a voip gateway line
Put Asterisk on it and somehow solve the issue with "Office 2 employees can call and receive calls from one of the office 1 city lines
"
don't know how it will turn out

Answer 1

VPN up and connect networks.
In one of the offices, which is better than number 1, raise the asterisk. City analog lines will have to be connected through gateways. Both gateways must connect via SIP to Asterisk. And softphones are not needed in such an implementation.

Answer 2

To begin with, I think you need to resolve the issue with "... dynamic public IP ..." (otherwise, how do you think VPN-build?! DynDNS is not an option ...) The ideal option would be, of course, "static" on both sides , minimally - "static" from office 1!
Then, connect 2 analog lines to Asterisk (you will need to buy an analog port board), everything else is decided at the level of working with a file with the Asterisk config ... VoIP gateways will be needed as end devices (by and large, then you can use ordinary telephones!).. .Enjoy!

Answer 3

I, like Alexander , would first of all be puzzled by statics, at least in one of the offices. How much is a white IP now for a beeline? 500 rubles per month?
Plus, even if there is an attachment to analog telephone numbers (like all customers know and are used to), there is a strong opinion that it would be time to migrate to SIP, which will make it possible to fully use the flexibility and scalability of Asterisk in the future. Take, for example, the fact that it will be possible to deploy an asterisk in any other geographical location and on a virtual machine, not to mention moving the office. Instead of buying a board www.pbxware.ru/catalog/platy_digium/analogovye_platy, buy SIP phones or SIP gateways.