I have one oracle server behind one ISA at each site and want to communicate oracle at both sites. Current configuration is as follows. Published oracle w 1521 port at each end Add protocol definition - > Oracle-1521 Install Firewall client on both oracle server Only have one public ip for both sites. Problems Two oracle can communicate when using only one ISA. Tnsping is get success. Sqlplus has problem when using isa at both ends. Could u pls help me on this issue? Thanks.