3850 DHCP excluded addresses problem

[Charles Rayer]

Hi Guys,

I'm running stacked 3850s on a LAN with serving several DHCP pools.

I have an issue now and again where they stop giving out addresses.

Looking at Show Ip DHCP Poo brings up a summary of all the pools and I can see that the excluded addresses have risen to such a point that it's exhausted the pool. But I haven't configured that many exclusions, the lease is generally set to 3 or 8 hours and there's definitely not that many people in the venue.

Example:

Pool Public :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 69
Excluded addresses : 109
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased/Excluded/Total
10.205.95.61 10.205.95.1 - 10.205.95.254 69 / 109 / 254

On this range I have excluded 11 addresses and the lease is set to 3 hours

I have to delete the pool and add it in again when the Excluded addresses reaches a point that no-one can join the network.

Is this a bug or am I missing something?

Thanks for reading

[Georg Pauwen · Accepted solution]

Hello,

assuming you are not using database agents, do you have:

no ip dhcp conflict logging

configured on the 3850 that serves as the DHCP server ?

Can you post the configuration of the DHCP server switch ?

[Charles Rayer]

Hi Georg,

Thanks, you steered me in the right direction and I found a great page that shelped me immensely.

http://blog.ipspace.net/2007/08/dhcp-conflict-logging-true-story.html

[Georg Pauwen]

Charles,

good article indeed. How did you eventually solve this ?