Understanding GTM Wide IP Operations
I would like to share my understanding for the GTM Wide IP load balancing methods to confirm if this correct or not for a specific configurations:
- GTM is integrated with LTM in HQ and DR sites.
- I have Wide-IP configured with around 10 Pools, each pool having 2 different virtual servers (One in HQ and the other in the DR) the virtual servers of the pools in both HQ and DR are having the same IP address but with different service ports.
-The load balancing method at the Wide IP level is round robin, my understanding that the DNS responses will round robin between all the 10 pools configured under the Wide IP.
- The load balancing under the pool level is Global availability so it will resolve the query with the IP of the first member order in the pool (HQ Virtual server in my case) and if it is down it will resolve with the IP of member order 2 of the pool (located in DR site).
- Incase that the 2 pool members are down in the pool, it will fail to return DNS if it is the configured fallback LB method.
- Incase no Fallback method configured, and both pool members are down the GTM still can respond from the Bind (zonerunner records added by default when wide-ip configured) if the DNS profile Unhandled Query Actions configured to Use BIND.
Please can some confirm my understanding, i just want to understand the operations regardless if the configuration are not accurate or not recommended.
gtm work like you say, if the dns profile of the gtm dns listener does not disable the dns bind function, wideip fallback mothod set to Return to DNS, if all gtm pool members down, it will use dns bind round-robin to response dns request
If you are not clear, you can apply for 30 days trial BIGIP-VE，Do experiments to simulate some extreme scenarios, such as：
1. disabled wideip, will it cause fallback method Return to DNS, work use dns bind function ok ?
2. althernatte method set to None, fallback method to None, when all gtm pool members down, does gtm return to dns response?
3.disabled gtm pool or disabled gtm pool all members, or disabled gtm server virtual server, what will gtm work?