GTM and cluster

Well, strange things happen. I don't really know what was cause of my problem - v13.0.0HF2 bug, coincidence or sun activity...

Anyway my Sync Group and HA Sync Failower mariage refused to work. Everything looked perfectly OK:

• Same versions of TMOS on both devices
• Correct certificates
• Working iQuery communication

Still GSLB changes made on one device were never propagated to another.

cid.id number was increased separately on both and never matched.

After hours of futile fight I decided to chose hard way - strat from scratch:

• Remove whole GSLB config from both devices (I wonder if there is some easier way that deleting all objects via GUI - probably just cleaning bigip_gtm.conf and do load sys config gtm-only)
• Break DSC (Standby set to Forced Offline), clean floating object on Standby

Then I changed order of battle:

First configured GSLB objects:

• Server that contains DeviceA set with self IP of device to which another GTM will be added
• Server that contains DeviceB set with self IP of device that will be added to Sync Group as second GTM
• Then perform gtm_add from DeviceB

So far so good, syncing changes started to work both ways.

Then I started to recreate cluster - and there strange things started. After adding DeviceB as Peer suddenly cid.id for gtm device_group was reset - from let's say 100 to 2 on both devices.

Then errors started to pop out in gtm log:

• Encountered error while processing mcp message at ../gtmdb/db_devicegroup_device.c:325 : Unable to associate a device with an unknown group
• iqsyncer errors showed up on DeviceB

But still syncing changes kept working.

Then I created Sync Failover group and synced both device.

After this operation changes in GSLB setup are still propagated both ways (sure completely separate from ConfigSync operations).

So again I am puzzled what I did wrong during first attempt? My main suspect is this cid.id reset after configuring Peer... but I am not sure.

I think as well that Active-Passive cluster can be used when separate DNS listeners are needed per Data Center - just set listeners using self IP subnets that are specific to DC - those will not be synced via Config Sync but still covered by GSLB sync.

Of course DNS Listener configured on floating IP subnet can as well be used - then you can have everything in one package - syncing what is necessary between DSs and have DC unique part.

Piotr