Forum Discussion
williamcs
Nimbostratus
Nimbostratussource address persistence maximum session timeout
Understand that the source address persistence session timeout will start once the session goes idle (no traffic). 1.What is the maximum timeout setting? 2.The default value is 180s, any possible i...
williamcs The following are the answers to your questions.
1. Based on F5 documentation the value can be within range 1 and 2,147,483,647.
2. The only real downside I see to increasing the timeout value higher than the default is if you have a high connection virtual server you could theoretically reach a very large persistence table which would cause performance degredation.
Hello,
Generally speaking on the source address persistence, LTM creates a new persistence record as netmask is /32 which makes a new record for each request. As the number of sources increases, the number of records created and saved locally in the persistence table increases which might be an issue. So such a large list of persistence records can become a resource issue for LTM.
To avoid this issue, you can create a custom source address persistence profile and change the mask to (for example: /24) to avoid creating many entries. but you will face another issue, and more users will be identified as coming from the same source.
So based on the above, if you increased the timeout, the entries will be saved for a longer time, and the table will become very large which might be resource intensive based on the number of requests.
I'm not seeing any articles mentioning performance issues when increasing the timeout, but it logically might have an issue because these entries are saved locally on F5, and the more sources access the service with (a long timeout) the more entries will be saved on F5 without clearing the old ones.
Thanks,