We have a branch with two Linksys SPA942 voip phones connected via a vpn to the main site SPA900/SPA400 ip pbx. Currently using Netgear VPN routers, the phones register/connect with sip just fine, but features such as auto provisioning and voice mail do not work. For these to work requires multicast packets to pass over the VPN. Netgear does not seem to support this.
Can anyone suggest reasonably priced VPN routers that support multicast over VPN?