To often administrators can make the mistake of performing maintenance on their Database Availability Group without performing the proper checks and balances to ensure that all will be well when replication is enabled once again. This post will go over the scenario of moving your replication to a new subnet in the event of a DR site build or some other scenario that may force a move to a new subnet.
A couple of items to remember when dealing with DAG networks:
- DAG replication network must be on the same subnet or on two subnets with a static route as the rest of the Exchange servers it will be replicating with.
- The replication nic should be second in the preferred order of network cards.
- The DAG network nic card should not have a gateway IP configured, and at no time should be able to communicate with the MAPI network over its replication dedicated nic card.
- If the replication network experiences an issue, the MAPI network will be utilized and replication will continue.
Once these items have been verified, you can suspend replication on the database COPIES you wish to change replication for. Once suspended, you can then change the NIC IP address settings to the new replication network.
Several items must be verified before attempting to resume replication on the databases.
- You must verify that there are no network connectivity issues on the new replication network.
- Test this via ping and telnet between the Exchange servers on the following port:
- If there is a firewall between the exchange sites, ANY communication from ANY Exchange server to ANY other Exchange server in the other site should be allowed on your Firewall.
Once the above is verified, you can resume replication on the database copies. At this point, replication should be occurring over the correct network. To verify this, download Wireshark and verify on the replication interface that you see traffic to from the exchange servers using port 64327. If you don’t, recheck your basic network connectivity on your new replication network.