Excluded Dhcp address are showing more than I excluded

[ahmedbishry]

Dear All,

I have a Cisco Catalyst 4506-E Swtich,

I configure it as a DHCP and gw for the Wireless Cisco AP through the WLC 5508,

the DHCP pool reached the maximum limit

I run the Show ip dhcp pool (pool name)

it's show the below result

GIR906.PCIRQ.DC.CR.1#show ip dhcp pool 406

Pool 406 :

Utilization mark (high/low)    : 100 / 0

Subnet size (first/next)       : 0 / 0

Total addresses                : 126

Leased addresses               : 76

Excluded addresses             : 54

Pending event                  : none

1 subnet is currently in the pool :

Current index        IP address range                    Leased/Excluded/Total

0.0.0.0              10.114.42.129    - 10.114.42.254     76    / 54    / 126

You can see the Excluded IP are 54

i check the excluded range it was

ip dhcp excluded-address 10.114.42.245 10.114.42.254

you can see that i'm exclude only 9 ip address

please advise,

thanks in advanced,

[cadet alain · Accepted solution]

Hi,

can you do a sh ip dhcp conflict.

Regards.

Alain

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[ahmedbishry]

Dear Cadet,

many thanks for your reply, I really appreciate your effective troubleshooting,

you are wright I found around 44 conflict on this dhcp pool address, as below

10.114.42.134     Ping               Nov 08 2012 10:46 AM

10.114.42.130     Gratuitous ARP     Nov 07 2012 01:15 AM

is this normal ?

What is the reason behind all these conflicts?

Ahmed,

[cadet alain]

Hi,

was your switch ever reloaded? can you ping the first one and then do sh arp to see its mac and then trace it.

Regards.

Alain

Don't forget to rate helpful posts.

[ahmedbishry]

Dear Alain,

should I reboot the SW ?

can you please tell the reason behind this conflict?

Thanks

Ahmed

[Marius Ilie]

A bit late, however, for others who will encounter the issue, IP conflicts appear often, you can see them with:

sh ip dhcp conflicts

The addresses in conflict are removed from the pool so they will not be used until conflicts are cleared. to clear them use:

clear ip dhcp conflicts *

Hope it helps

[Matt Crosby]

Is there a way to prevent this?

I have several switches giving out DHCP. They often max out their scope due to these excluded addresses. I've been doing the clearing but they return. 

Isn't there some lease setting or option to release these or clear them automatically after a certain amount of time?

[Marius Ilie]

Please check the following:

https://supportforums.cisco.com/community/5941/eem-scripting

Marius