Below I m showing my DNS configuration (Bind version 9): $ORIGIN 1.2.3.3.e164.arpa. * NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@server1.com!" . $ORIGIN 8.8.5.2.1.2.3.3.e164.arpa. * NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@server2.com!" . When I use DIG "1.8.8.5.2.1.2.3.3.e164.arpa" or " 1.8.8.5.3.1.2.3.3.e164.arpa", I don´t have problem. But When I try "1.8.8.3.2.1.2.3.3.e164.arpa" DIG don´t obtain resolution. I see that I need to add in DNS the tree between 1.2.3.3 and 8.5.2.1.2.3.3: $ORIGIN 2.1.2.3.3.e164.arpa. * NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@server1.com!" . $ORIGIN 5.2.1.2.3.3.e164.arpa. * NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@ server1.com!" . $ORIGIN 8.5.2.1.2.3.3.e164.arpa. * NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@server1.com!" . I have a lot of servers and this is not scalable, then I can´t use the tree between 1.2.3.3 and 8.5.2.1.2.3.3. Is there another configuration that I don´t need to use the tree between 1.2.3.3 and 8.5.2.1.2.3.3?