Swapping IP addresses between network interfaces dynamically

As a systems administrator, you may at some point experience a problem with a network interface card on one of the PowerHA® SystemMirror® cluster nodes. If this occurs, you can use the dynamic communications interface swap feature to swap the IP address of an active service network interface with the IP address of another active, available network interface on the same node and network. Cluster services do not have to be stopped to perform the swap.

About this task

You can use this feature to move an IP address off of a NIC that is behaving erratically without shutting down the node. It can also be used if a hot pluggable communication device is being replaced on the node. Hot pluggable NICs can be physically removed and replaced without powering off the node.

This feature can also be used to move the persistent IP label to another network interface.

Make sure that no other PowerHA SystemMirror events are running before swapping a network interface.

To dynamically swap an IP address between communication interfaces:

Procedure

  1. Enter smit cspoc
  2. In SMIT, select Communication Interfaces > Swap IP Addresses Between Communication Interfaces and press Enter.

    SMIT displays a list of available service interfaces. It also displays those interfaces that have persistent labels placed on them, but are not hosting service IP labels. This allows you to move the persistent label to another interface.

  3. Select the service communication interface you want to remove from cluster use, and press Enter.

    SMIT displays a list of available boot interfaces.

  4. Select a boot interface and press Enter.

    The Swap IP Addresses Between Communication Interfaces menu appears.

  5. Verify the service IP label, and the boot IP label you have chosen. If this is correct, press Enter.

    SMIT prompts you to confirm that you want to do this operation.

  6. Press Enter only if you are sure you want to swap the communication interface.

Results

After the swapping of IP addresses between communication interfaces, the service address becomes an available boot interface. At this point, you can take action to repair the faulty network interface card. If you have a hot pluggable network interface card, you can replace it while the node and cluster services are up. Otherwise, you will have to stop cluster services and power off the node to replace it.

If you have a hot pluggable network interface card, PowerHA SystemMirror makes the interface unavailable when you pull it from the node. When the new card is placed in the node, the network interface is incorporated into the cluster as an available boot IP label again. You can then use the dynamic network interface swap feature again to swap the IP address back to the original network interface.

If you need to power off the node to replace the faulty network interface card, PowerHA SystemMirror will configure the service and boot addresses on their original communication interfaces when cluster services are restarted. You do not need to use the dynamic network interface swap feature again to swap the interfaces. PowerHA SystemMirror does not record the swapped interface information in the AIX® Configuration Database (ODM). Therefore, the changes are not persistent across system reboots or cluster restarts.

Note the following restrictions:

  • The dynamic IP address swap can only be performed within a single node. To move an IP address to another node, move its resource group using the clRGmove Resource Group Management utility.