Configuring custom HA replication interfaces

Advanced users can, if required, configure different replication interfaces to the default for high availability (HA) configurations.

About this task

By default, the eth21 interface is used for data replication in an HA configuration, but you can specify a different interface, if required. You can configure different interfaces on each appliance, for example, you could specify eth23 as replication interface on one appliance, and eth22 on the other. You should choose an interface of at least 10 Gb; the performance of a 1 Gb replication link is likely to be poor.

If you have added disaster recovery to your HA configuration, you can also specify a different interface for DR replication to the default eth20 interface. If you do have DR in your HA configuration, both HA appliances must use the same interface if you are using a floating IP address to replicate data. If you are not using a floating IP address, you do not have to use the same interface on both appliances..

Procedure

To configure a non-default HA replication interface:
1. Cable your custom interface. For example, if you intended to use eth23 for HA replication on both appliances, you should connect eth23 on both appliances in your HA group, either by a direct cable or a switch.
2. Enter the IBM® MQ administration mode on both appliances by entering the following command:
  
  mqcli
3. Set up your custom interface by using the following command on both appliances:
```
sethalink -r IP_address
```
  Where IP_address is the IP address of the interface to be used for replication. You must specify the IP address using ip v4 dotted decimal notation (for example, "192.0.2.8"). The two IP addresses (one for each appliance) should be in the same subnet. The interface that you specify on each appliance must meet the following requirements:
  - The IP address specified must map to a valid local interface or aggregation interface (you cannot specify a VLAN interface).
  - The local interface must be at least a 10 Gb link, otherwise you are warned.
  The command fails if the HA configuration is already active.
To check the configuration of your HA replication link, enter the following command:
```
dsphalink
```
The current settings for HA replication interface are displayed, for example:
```
Replication:		192.0.2.8 (lo)
The dsphalink command succeeded.
```
To revert to the default configuration of using eth21 for the HA replication link:
1. Cable your eth21 interfaces on each appliance together, either directly or using a switch.
2. Enter the following command:
```
sethalink -d 
```
  The command fails if the HA configuration is already active.
To configure a non-default DR replication link for your HA configuration:
1. Make the necessary hardware configuration to connect the appliances in the HA group to the DR appliance.
2. Enter the IBM MQ administration mode on both HA appliances by entering the following command:
  
  mqcli
3. Set up the custom interface by entering the following command on both HA appliances:
```
setdrlink -r IP_address
```
  Where IP_address is the IP address of the interface to be used for replication. You must specify the IP address using ip v4 dotted decimal notation (for example, "192.0.2.8"). The interface that you specify on each appliance must meet the following requirements:
  - The IP address specified must map to a valid local interface or aggregation interface.
  - The local interface must be at least a 10 Gb link, otherwise you are warned.
  - You must select the same interface for both appliances in your HA group if you are using a floating IP address to replicate data. If you are not using a floating IP address, you do not have to use the same interface on both appliances..
  The command sets a new interface from that moment forward, so that any crtdrprimary and crtdrsecondary commands set up a DR configuration using the newly specified interface. Any queue managers configured to use DR before this point will continue to use the default interface, rather than the new one, unless you remove and recreate the DR configuration for those queue managers.
To check the configuration of your DR replication link, enter one of the following commands:
- To view the DR replication link for a particular queue manager:
```
dspdrlink -m QueueManager
```
  The IP address and interface name currently configured for that queue manager are displayed, for example:
```
QM1			10.120.5.42  (eth21)
The dspdrlink command succeeded.
```
- To view the default setting, and the settings for existing queue managers:
```
dspdrlink
```
  Fore example:
```
Default		10.120.10.100 (eth20)

QMGR 		     DR Interface (Name)
----			-------------------
QM1			10.120.5.42  (eth21)
QM2			10.120.6.42  (eth22)

The dspdrlink command succeeded.
```
To revert to the default configuration for the DR replication link:
```
setdrlink -r
```