Configure Advanced Routing in Router Cisco RV042

We have ap roblem with this asterisk box because the router sometimes "DONT KNOW" where to send the packets and then we got a problem between the incoming and outgoing calls, our [login to view URL] is well configured, and the problem is the route, because if we switch off and on the router it is working normally until three days. Basically the problem is between this scenario: WAN1: [login to view URL] (full ip address DSL updating by no-ip ddns) WAN2: [login to view URL] ([login to view URL] double nat address cablemodem) the problem basically is that suddenly the asterisk is sending the invite by: INVITE sip:87XXXXX@[login to view URL] SIP/2.0 but sometimes the packet is answering by: [login to view URL] with an SIP/2.0 401 UNAUTHORIZED CUT HERE (THIS IS ANOTHE EXAMPLE ON THE SAME WEEK) the 201.141.* is the cablemodem wan ip address and the 187.207.* is the DSL as you can see the problem is that im sending the registry by one ip address and receiving from another INVITE sip:87XXXXXXXXX@[login to view URL] SIP/2.0 SIP/2.0 401 Unauthorized Via: SIP/2.0/UDP VOIPPROVIDERIP;branch=z9hG4bKa688.a75e94f3.0;received=VOIPPROVIDERIP Via: SIP/2.0/UDP VOIPPROVIDERIP:5070;branch=z9hG4bKa688.c9391e21.0 Via: SIP/2.0/UDP VOIPPROVIDERIP;branch=z9hG4bKa688.975e94f3.0 Via: SIP/2.0/UDP [login to view URL];rport=5060;received=[login to view URL]