Re: ipsec vpn cisco phone
that is not possible with IPsec VPN.
an IPsec VPN is between different layer 3 networks.
if you really want this you need to create a streched layer 2 network (via vxlan or l2tp or such)
i would advise you to look into just getting your phones working via layer 3, so allow that the cisco pbx can accept phones in other networks.