The following error is shown on a DS/OpenDJ replication server (in the Errors and Replication logs):
[21/Mar/2017:11:43:29 -0500] category=SYNC severity=SEVERE_ERROR msgID=10 msg=In Replication server Replication Server 8989 18989: replication servers 192.0.0.0:8989 and 203.0.113.0:8989 have the same ServerId : 12345
This error can occur if you cloned the configuration from one replication server to another; however, the most common reason is having multiple IP addresses.
For example, in the scenario where replication server (server1) is on a host that has two IP addresses (192.0.0.0 and 203.0.113.0) and connects to another replication server (server2), this error would be logged on server2 if server1 connected to it via a different IP address than the one used when configuring replication initially.
This issue is considered a severe error because it suggests that a fundamental aspect of the replication topology is being violated; namely, that every server in the topology has a unique server ID.
This issue can be resolved by configuring the source-address property on your replication servers to just one of the interfaces; you should choose the one that is configured with the FQDN being used in the replication setup. That way you should get connections coming consistently from the correct address.
You can use the dsconfig set-replication-server-prop command to make the appropriate change. For example, the following command configures the server at ds1.example.com to only make outbound replication connections from the NIC with the address rs.example.com:
$ ./dsconfig set-replication-server-prop --provider-name "Multimaster Synchronization" --set source-address:rs.example.com --hostname ds1.example.com --port 4444 --bindDN "cn=Directory Manager" --bindPassword password --no-prompt --trustAll