DHCP excluded addresses that I did not exclude

[dstafford90]

We have a our DHCP server setup on one of our core switches for one of our smaller lesser used networks. It has been functioning fine until yesterday. It was behaving like we had run out of addresses. After doing some digging it "kinda" had. 

When running show ip dhcp pool name, it shows Leased 51 / Excluded 184 / Total 254. 

I have only excluded 20 of the addresses. ip dhcp excluded-address 10.x.x.1 10.x.x.20

What could cause the switch to exclude the other 164 addresses? Any insight would be greatly appreciated!

[Mark Malone]

Can you post the dhcp config off the switch, if its not set to exclude addresses and it is,  you may have a software issue and show ip dhcp pool

also software version and switch model

[dstafford90]

Thanks for your response.

Software Version: 12.2 (58) SE2

Model: 3750x (WS-C3750x-48T-S)

I have attached screenshots of the commands. 

[Mark Malone · Accepted solution]

First thing I would do is remove the dhcp and re-apply it , 9 times out of 10 this fixes the issue

That's a decent enough image your on and obviously your config is ok if that's all in place

Other than that if its still the same I would change IOS version

[dstafford90]

I will try that this afternoon when the pool is not needed. We are currently fine with addresses at the moment.

[Mark Malone]

did re-applying the pool work or is it still showing excluded range

[pwwiddicombe]

See if "clear ip dhcp conflict * " will recover addresses.

If for some reason a conflict has been detected, the DHCP will automatically block out the conflicting addresses - not sure if/when conflicting addresses are automatically released eventually.

[dstafford90]

I will try this when the ones that are currently using the excluded addresses have time to time out. But it makes complete sense as to why they would be excluded. 

[soporte spconnet]

Hi dstafford90,

I have the same issue, what was the solution for you problem?? thanks a lot, regards!

[dstafford90]

Removing and readding the DHCP pool resolved our issue. We had some IPs that got excluded again but that was because they were still in use. After a few days I ran the "clear ip dhcp conflict *" command and that took care of those since they were no longer in use.  

[nnagraju9]

@pwwiddicombe 

"clear ip dhcp conflict"  command worked.

Thank you very much.

[j.beckner]

It doesn't look like they are ever released.  My client had about half the DHCP pool excluded because of conflicts going back a year to the last reboot.

[dstafford90]

It cleared almost all of them. I checked the leases before I removed the pool and it had 19 leased. After re-adding there are 19 excluded. So I think what Pwwiddicombe said would be right as well. That it detected that those were already used and excluded them. 

Thank you for your assistance!