Investigating network issues
GoldenGate is heavily dependent on a fast and reliable network between a source and the target database; without this, data replication cannot take place. Furthermore, if your network fails, the Extract, data pump, and Replicat processes may not necessarily ABEND, so you could be running blind.
TCP/IP
By default, the GoldenGate Manager uses the TCP port 7809. This starts a server collector process on the port 7819. As the load increases, the server collector dynamically chooses a port in the default range or from that specified in the range configured by the Manager process' DYNAMICPORTLIST parameter. The Manager can dynamically spawn up to 256 additional processes running on dedicated ports, which may or may not be open and available to the operating system.
One obvious check to confirm connectivity between hosts is to use the Linux ping utility. However, ping uses the Internet Control Message Protocol (ICMP), which can also be blocked by firewalls. So, to confirm...