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New Member

AP unable to get IP address after WLC is rebooted

Hi all,

I had configured a Cisco 5508 series WLC. The APs used are Cisco 3502 LAP. The APs are configured to use DHCP for this ip addresses.

We had configured the DHCP server on the 2 Windows AD server previously and the APs were not able to get an IP address when the WLC was rebooted. To isolate the cause, we configured the DHCP server on a cisco 6500 switch. When we reboot the WLC, most of the APs are not able to grab an IP address. We had to remove and reconfigure the DHCP pool on the cisco 6500 for the APs to capture the IP addresses.

My colleague had feedback that they gotten a message that the DHCP pool had been used up. We tried to do a "show ip DHCP pool" but the switch did not recognise the command. IOS version used is Version 12.2(50r)SYS2.

We had a problem with the wireless client getting ip addresses from the windows DHCP server previously but problem was resolved after we disabled the DHCP proxy on the WLC.

What we are curious is why was the DHCP pool fully used on the Cisco switch and how could we check the number of addresses used other than running "show ip dhcp binding" and doing a count of the IP addresses?

Also why did we have to disable the DHCP proxy on the cisco WLC for the wireless clients to be able to get an IP address from the windows DHCP server?

We seem to be facing a number of problems with the DHCP functions for the wireless setup. Anything in particular that we should take note?

Thanks.

Everyone's tags (7)
1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

AP unable to get IP address after WLC is rebooted

in general, DHCP proxy enable vs disable shouldn't be matter if msoft server is DHCP.

do you use AP group, IG group, AAA override, frequent L3 roaming.

Run dhcp debugs on WLC and AP and post it here.

5 REPLIES
Hall of Fame Super Silver

Re: AP unable to get IP address after WLC is rebooted

Make sure the APs are in it's own subnet and not mixed in with user. Set the lease to 4-8 hours if the dhcp scope is for the APs only. I don't like using the switch for dhcp and also make sure you have an ip helper address on the ap subnet pointing to your dhcp server.

Sent from Cisco Technical Support iPhone App

-Scott
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Hall of Fame Super Silver

Re: AP unable to get IP address after WLC is rebooted

Also, plug a laptop in on one of the ports and see if that device gets an ip.

Sent from Cisco Technical Support iPhone App

-Scott
*** Please rate helpful posts ***
Bronze

Re: AP unable to get IP address after WLC is rebooted

If the access points are not able to get an IP address from the external DHCP server it would not be an issue with the WLC.

Please connect a PC to the same port where you have one of the access points with the issue and check if ther PC is able to get an IP address from the correct DHCP server and in the correct range.

New Member

AP unable to get IP address after WLC is rebooted

Hi Guys,

Thanks.

I will try and revert on the findings

Regards,

Victor

Cisco Employee

AP unable to get IP address after WLC is rebooted

in general, DHCP proxy enable vs disable shouldn't be matter if msoft server is DHCP.

do you use AP group, IG group, AAA override, frequent L3 roaming.

Run dhcp debugs on WLC and AP and post it here.

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