DHCP badLeases

[Moudar]

Every time when my 5520 WLC restart for some reason, many APs continue to be down because they don't get IP address from the DHCP server.

DHCP server problem is getting many bad-leases, so every time i need to clean the bad leases first, then all my APs getting IP address and getting up. Not all APs, for example: I have 1000 APs 700 get an IP address but 300 don't (bad-leases).

Any one have idea about the reason?

Bad-leases happens only when many APs ask for IP addresses at the same time!

[Arshad Safrulla]

Sounds more like a DHCP server issue, I have worked on bigger deployments than this and very rarely had DHCP related issues. May be your DHCP server is not sized properly.

If it is sized properly and the DHCP server OEM claims that it is working as expected, then your best would be to simulate the scenario again, capture the packets and analyze them may be with the help of TAC.

[Moudar]

I will test the solution which can be found on the link below and get back with results:

Solved: AP or controller reload causing Windows DHCP BAD_ADDRESS - Cisco Community

[Scott Fella]

Bad ip address only happens when using a Microsoft DHCP server.  The issue is that when an ap no longer can communicate with the controller, it will reboot, then the dhcp server will provide the same ip address but the ap responds asking for a new one.  This makes the MS dhcp server mark the dhcp ip as bad.  You can search "cisco ap microsoft dhcp bad address" and you will find what others have done or work arounds.

I actually opened a bug on this a long time ago.  They did come up with a fix and this was the solution.

config ap dhcp release-override

[iores]

@Scott Fella But why DHCP doesn't offer another IP address after it marks the first one as BAD ADDRESS?

[Moudar]

After using The command on WLC 5520:

config ap dhcp release-override enable all

Restarting a 5520 WLC with about 500 APs, succeded with no Bad_Addresses on Windows DHCP.