Can GTM redirect DNS requests to external host?

A few answers/comments to your questions.

 

 

1. The GTM server statistics are gathered through probing. I am not sure why they would be different than LTM statistics, so if it is of concern, you will likely need to open a subcase with support and provide additional configuration information.

 

 

2. LB_FAILED means that no answer to the DNS request was provided. The load balancing modes you have selected will determine whether or not an answer will be returned and this iRule will be executed. One thing to note is that your fallback load balancing method is the most important in determining this as some methods will use any pool member possible, even if unavailable (red/yellow). For example, if your wide IP has one pool, you could select the "None" fallback load balancing method to have the iRule executed. If you have multiple pools, I would suggest reading the load balancing section of the manual to determine exactly which load balancing mode to use. Configuration Manual, Chapter 7 – “Using the fallback load balancing method”

 

 

In regards to the dig question, you’ll want to make sure you dig from a box that is not the GTM. Your dig command may look like: dig @

 

This command should clearly return the CNAME as the result instead of a pool member address when the iRule is executed. If you have additional questions about dig, I suggest taking a look at the dig man page. Bigpipe can not be used to do digs with GTM. Also, I’d suggest checking out the DNS & BIND book, Fourth or Fifth edition, by O’Reilly. This should be able to answer any additional CNAME questions you may have.

 

 

3. It sounds like the Last Resort Pool feature may do what you are hoping to achieve here. Take a look at the Configuration Guide Manual, Chapter 8 – “Setting the last resort pool”

 

 

Thanks.