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FAQ 143: ClientTimeout setting explainedCategory: RedirectIP function | Updated: 04/06/2012 9:44 PM
ClientTimeout= is the number of minutes that must pass without any DNS requests from the client, after which that client is considered gone from the network.
When a client is gone they are removed from the online clients list, this inherently de-authorizes the client, re-enables the block, and executes a LeaveAction if set.
After this timeout, a client who starts generating DNS traffic again (regardless of same or different IP lease) will get redirected again.
Consider that depending on location, the typical stay (or time spent online) of a client is different.
For example, at a library the typical stay might be 1 hour or more whereas at a fast food place the typical stay might be only 20min.
In many cases you may want to extend the default "ClientTimeout=20" minutes to be equal to the typical stay, this can avoid client frustration of being redirected before their stay is over.
Setting the ClientTimeout appropriately avoids wasting your concurrent client license on client's who are no longer there.
Ideally, your DHCP lease time would be set the same as the ClientTimeout value, this avoids wasting IP address allocations on clients who are no longer there.
What the ClientTimeout setting is not...
Some administrators have asked how to force clients to be redirected after a set time;
example A) the client is paying for 30min. of Internet after which they should then be redirected again,
or example B) a nearby/neighborhood resident is using your free hotspot continually.
A) The ClientTimeout is intentionally not implemented as a ForcedTimout.
Lets say the client is granted use of the hotspot for a half-hour.
Later the half-hour expires but the end-user was still in the middle of composing a message in webmail, or ordering something online, or writing in a comment box or forum.
When the user clicks send, their work/progress may be lost because they may be redirected.
The redirect cannot be guaranteed because different OS's and browsers will very likely cache the DNS lookups and/or web-pages.
Implementing this would frustrate end-user's either because they lost work or because an inequality is created when other users seemingly get more access time.
Regardless, this is not terribly friendly and makes some people very upset.
B) When the DNS Redirector software is restarted, the status of all clients is forgotten and all clients are treated as new.
Depending on the client OS and browser, recent DNS lookups and/or web-pages may still be accessible for a short time.
Certainly, when a client visits a unique site they haven't visited before or closes and opens their browser they would get redirected again.
You can restart (or stop) the DNS Redirector service nightly, effectively kicking off all clients,
either by checking "Run updaterdone.bat when done" (if using Updater) or by adding a scheduled task to run updaterdone.bat directly.
If experiencing trouble from a particular client you may consider blocking their MAC address in the access point or router, but be aware that savvy users may be able to change their MAC to something else.
Some hotspot operators choose to display a code, either on a sign within their business or on a receipt, which patrons enter on the redirect page in order to gain Internet access.