Monday, 29 July 2013 09:16

Modify the DAG Replication Network Settings (Subnet, NIC IP Address etc…)

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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,

  1. Extend the existing replication VLAN subnet to accommodate more DAG members
  2. Migrate the replication network to another VLAN as part of some network revamp

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.

  1. Modify the subnet mask on the replication NIC settings.
  2. Open the EMC and navigate to DAG Configuration window (Organization Configuration -> Mailbox; then click on Database Availability Groups tab in the right pane of EMC).
  3. Modify the subnet mask on DAG Network settings, follow below steps
    1. Click on the DAG name, for which you want to modify the network settings
    2. Open the properties of the DAGNetwork, that used for replication (private).
    3. Delete the existing subnet (only when you are modifying the subnet range) and apply the change
Note – You will not be able to directly modify the netmask, and it will through the below warning message if you do so,
Set-DatabaseAvailabilityGroupNetwork
Failed
Error:
Subnet '10.0.0.0/27' can't be set because it conflicts with existing subnet '10.0.0.0/29'. When setting subnets, the subnet must exactly match a subnet that is configured for a network on the server.
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)
4.  Verify the replication.

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.

  1. Open the EMC and navigate to DAG Configuration window (Organization Configuration -> Mailbox; then click on Database Availability Groups tab in the right pane of EMC).
  2. Add the new IP range and subnet mask on DAG Network settings, follow below steps
    1. Click on the DAG name, for which you want to modify the network settings
    2. Open the properties of the DAGNetwork, that used for replication (private).
    3. Add the new ip range and subnet mask as an additional subnet and apply the change

Note – you may receive the below warning,

Set-DatabaseAvailabilityGroupNetwork

Completed

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.

-Praveen

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