Forum Discussion
Ed_Powell_45353
Nimbostratus
NimbostratusGTM 9.4 and WideIP persistence question
So, I can use persistence on the WideIP level to associate an LDNS IP with a VIP. Okay, great.
My question is about the TTL we specify. Is it x number of seconds after the first DNS lookup, or does it refresh the TTL on every lookup from the LDNS?
What I'm hoping for is the latter, so we can keep IPs going to the same place, and not have to worry about them getting a different IP every hour (unless, of course, they haven't made a DNS lookup within that hour). If its the absolute x number of seconds and then kicked out of the persist definitions, can an iRule be employed on the WideIP to do the TTL refresh that I want?
4 Replies
- I know I've tested this somewhere along the line... I believe each source is stored in a table, so it's unique to each hosts lookups... I believe it gets reset on each lookup.. not just the first lookup... don't take that as gospel, I'll have to check my notes tomorrow..
You have the option to set that ttl to a pretty darn long time length... so it really shouldn't be an issue either way...
So no need for an iRule here unless i'm not understanding what you're looking to accomplish.. 
Ed_Powell_45353If you could get back to me with those notes -- if the TTL does get reset with each lookup, that would solve my problem.
Even if the TTL can be set to an absurdly-large value, if it doesn't get reset with each lookup, there's still the possibility of a lookup returning a different IP from one second to another when that TTL times out, and we want to avoid that where possible.- Ed_Powell_45353Cheers! Actually, I was about to do some parsing of two ldns.gz files (each an hour apart) to see if I could find any that had refreshed. Obviously, having someone confirm this was a lot easier. :D
- Indeed, remember you can shorten the time that ldns.gz is written by shortening the metrics caching time... but I wouldn't make it too short.. 5 mins or so tops...
