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GTM Wideip and pool persistence

sathish_2826
Nimbostratus
Nimbostratus

Hi there , please help me understand the gtm wideip and pool persistence,

 

gtm wideip persistence — this tells a specific user how long you will stick with the same pool member for dns queries

 

gtm pool TTL: this tells the specific user, how often you would need to query the gtm for dns resolution,

 

for instance, if I connect to a wideip and gets a pool member as response, 10.10.10.10, assume that I have enabled wideip persistence as 3600 s, and pool ttl as 15 sec,

 

I will likely to get 10.10.10.10 for 1 hr, but for every 15 seconds a dns requests sends to wideip to see if the member is still active, is this accurate understanding?

 

please confirm

 

 

 

 

 

4 REPLIES 4

Simon_Blakely
F5 Employee
F5 Employee

> I will likely to get 10.10.10.10 for 1 hr,

 

The BigIP DNS will still return 10.10.10.10 to your query for 1 hour after the last time you checked.

 

> but for every 15 seconds a dns requests sends to wideip to see if the member is still active

 

Your system will cache the DNS result for 15 seconds, and then if you ask for that fqdn again, it will check.

 

Note: DNS Persistence may not always work the way you expect.

 

K15594:  Overview of BIG-IP DNS persistence

 

K6082: BIG-IP DNS provides persistence records for a wide IP after a pool or data center is disabled

Thank you Simon

One another clarification, after setting the wideip persistence TTL to 3600 s, and pool TTL to 15 seconds,

 

When i access my application in periodic intervals, it just keeps flipping between 10.10.10.10 and 10.10.10.11, these are my LTM vips in the pool.

 

Tested this multiple times and as you said, it is very inconsistent,

 

Do you have any other thoughts on this Simon?

How are you checking resolution?

 

I would recommend a dig command for the wideIP directly to your GTM listener is the best place to start.

 

If you use your local device DNS resolver, you may end up going through different LDNSs to the GTM and getting different persistence records.

 

Remember that the DNS persistence record is for the LDNS that queries the GTM, which probably won't be your own IP address.