Forum Discussion

sathish_2826's avatar
sathish_2826
Icon for Nimbostratus rankNimbostratus
Apr 24, 2020

DNS query for GTM & LTM based URL's

Hi there, I have couple of questions, my URL is load balanced between two LTM's and one GTM on top of it, so when i hit the application in the browser, it goes to DNS, DNS delegates to GTM for reso...
application delivery
BIG-IP
LTM
cjunior's avatar
cjunior
Icon for Nacreous rankNacreous
Apr 24, 2020

Hi,

If your VS goes offline, the customers who got the previous available IP will fail until the TTL expire or cache flushes.

You should consider setting lower values ​​for TTL to have high availability for your application.

 

Regards

cjunior's avatar
cjunior
Icon for Nacreous rankNacreous
Apr 30, 2020

Hi,

When query response are persisted, LDNS/client (an IP range) will get same resolved IP during this persistence validity.

When you check to persist to WideIP and keep "Verify Member Availability" on pool marked, in case of persisted member goes unavailable during ttl persistence, BIG-IP should reselect a new member.

 

So, a DNS record TTL is to cache responses on client and TTL persistence is a BIG-IP DNS feature to keep clients routed to destination address they first got.

 

For more: 

https://support.f5.com/csp/article/K15594

 

Regards.