APM-DHCP Access Policy Example and Detailed Instructions

Hi,

We are testing this solution to handle our DHCP requests but have run into an issue where duplicate IPs are being distributed. 

Here is the scenario:

User1 connects and gets an IP address.

For whatever reason user1 disconnects, which queues up a DHCP release for their IP on the APM, and then before anybody else connects user1 reconnects and gets the same IP address they had previously. For some reason when user1 reconnects this does not trigger the APM to release the “DHCP release” for user1’s IP address.

User2 connects which triggers the DHCP release for user1’s IP address and user2 gets their own IP address

User3 connects and is assigned user1’s IP address, even though user1 is still using it, because DHCP thinks it is available.

It is mentioned in the article that “You can force the release of unused leases simply by configuring a BIG-IP service monitor to connect to your APM virtual server periodically.” I tried this with a health monitor, HTTP and icmp, checking the pool with the virtual server in it every 5 seconds to force the release of the queued up “DHCP releases” but that didn’t seem to work. I figured every 5 seconds would be plenty of time to release the address of a user who disconnects and reconnects right away.

Can you elaborate on this solution from the article:” You can force the release of unused leases simply by configuring a BIG-IP service monitor to connect to your APM virtual server periodically—the monitor doesn’t need to log in or anything, it’s just used to provoke a “connection event” to force the iRule to run.”

Or can you provide another solution to forcing the queued up “DHCP releases” to be releases?