Following on from my below email, I can now definately say the problem is not nat pings. Just to recap I am experiencing intermittent audio. It works when the phones have very recently registered, then sometimes theres one way audio and then sometimes no audio. Does anyone have any ideas what the problem could be or where I could begin to troubleshoot this? Hi, I have a strange problem. I have two grandstream budgetone clients on the same subnet behind nat registering with ser on a public address. Obviously their public addresses would be the same but they listen on different ports. When they initially register, I can the call,audio is transmitted and everything is successful. However sometimes theres only one way audio, other times theres no audio and then other times it works....I am guessing that this is because the nat router is forgetting the nat mapping so after a while when the nat mapping is "forgotten" and a packet arrives destined for a client, the router drops it.... Could someone verify this for me??...Am I on the right track?? I have the following settings in ser.cfg which I thought would keep the nat settings alive. modparam("registrar", "nat_flag", 6) modparam("nathelper", "natping_interval", 30) # Ping interval 30 s modparam("nathelper", "ping_nated_only", 1) # Ping only clients behind NAT I also increased the nat keep alives "pings" sent in the configuration settings of the grandstream phone....Any further ideas?? Regards, Pat. Send instant messages to your online friends http://uk.messenger.yahoo.com _______________________________________________ Serusers mailing list serusers(a)lists.iptel.org http://lists.iptel.org/mailman/listinfo/serusers