We sometime might have to modify the replication network settings to accommodate either more DAG members, or to completely change the replication network with an alternate IP range due to some network revamp etc. I have outlined the steps to which you can safely modify the NIC settings and the DAG replication network properties without any downtime.
There are basically 2 scenarios,
Extend/Modify the existing replication VLAN subnet to accommodate more/less DAG members
You can follow the below steps to extend the VLAN, it is always better to keep the databases active on limited number of servers during the operation.
Note: During the change, the database replication will be disturbed and will resume automatically once the changes are over. Ensure that the replication network IPs are reachable from each node in case if you find any replication issues after the changes.
Migrate / Change the replication network to another VLAN as part of some network revamp
In this, we will start with the DAGnetwork property modification.
Note – you may receive the below warning,
Subnet '10.0.0.0/27' isn’t present in the database availability group. It will be added to the database availability groups network , but it will have no effect until a corresponding subnet has been physically configured on a server in the database availability group.
d. Click on Add button and enter the new IP range and subnet mask and Apply the changes (e.g. 10.0.0.0/27)
3. Modify the replication NIC properties on the DAG member server with the new network IP address and subnet masks.
4. Verify the replication after an interval.
The process is simple and fairly safe, and not expecting any down time to the end users operations. However, it is recommended to take necessary precautions.
Share your comments/queries.