I have a customer with 15+ branches running in SRST mode. About half of the branches have a VPN tunnel through the internet, the other half are on directly on the MPLS (via a T1 or DSL/Net-VPN). I have a problem where each of the branches will randomly go into SRST mode, even though there is no evidence that the tunnel went down.
My keepalive on the gateway is set to 20 seconds, but the phones will take about 2 minutes to re-register with the CCM. This I can probably fix eventually, but I wanted to know if anyone else is running a gateway with SRST over a VPN to see if I need to modify my settings to prevent the site from entering SRST at all.
There are different ways to display the RTP packets sent and received by the ephone. You can determine whether the ephone can receive RTP packets from Cisco CallManager Express in these ways:
Issue the show ephone command on Cisco CallManager Express.
Browse the ephone ip address in order to check the call stream statistics.
Press the help (i or ?) button twice in quick succession during an active call in order to show the call statistics on the screen.
Normally, GRE over IPSec is the recommended solution for this one-way voice issue. If the remote VPN client cannot support the GRE tunnel, as is the case with VPN 3002 client software, you can still use policy routing to achieve two-way audio.
You can use Policy-based Routing (PBR) in order to force the ephone traffic through the encryptor. In order to do this, apply a static route to the remote ephone pointing at a loopback interface. Then use PBR on the loopback in order to set the next hop downstream of the crypto map.
This is a sample configuration:
crypto isakmp policy 1
crypto isakmp client configuration group RemoteUsers