[Serusers] DNS SRV problem

Hello: I have a SER proxy server, and 2 SIP-to-pstn gateways (GW1, GW2). I would like to provide redundancy with SER using DNS SRV entries. The scenario is: every call must be directed to GW1, and **only** if GW1 fails, these calls must be directed to GW2. I've created these dns entries in Bind: _sip._udp.my.service.com. IN SRV 10 0 5060 gw1.service.com. _sip._udp.my.service.com. IN SRV 20 0 5060 gw2.service.com. gw1.service.com. IN A 192.168.1.1 gw2.service.com. IN A 192.168.1.2 service.com. IN A 192.168.1.10 SER receives calls to "user1(a)service.com".com", and after a dns srv lookup it sends the call to gw1.service.com correcly. SER configuration is: if (uri=~"user1"){ rewritehost("my.service.com"); forward(uri:host, uri:port); break; }; But, if gw1.service.com is down, SER never tries to send the calls to gw2.service.com. SER never send INVITEs to the server with priority 20. Is it a SER limitation, or is it a configuration problem? Thank you, Mark I would like to provide failover redundancy with SER