WAP551 stops passing DHCP

[James Walton]

Hello

I have 4 WAP551s at one of our sites, and I have discovered a problem whereby they stop distributing/passing through DHCP addresses to clients. This happens roughly every 2 days, at which point I simply reboot them all and magically the clients get addresses again and everything is OK for another couple of days.

I don't think it's the DHCP server (Win 2012 R2) since it still gives out addresses on wired clients when this problem occurs.

I have upgraded them all to the latest firmware and tried running them in a cluster (single point setup mode) and separately with the same SSID. Problem occurs in both modes.

If I give my wireless interface a static IP, I get full network access, so I don't think there's any routing/switch config issues.

Any ideas please? They're under warranty but I have no Cisco technical support contract. I could try get them all replaced but it seems unlikely to be a hardware fault with all 4.

[Jerry Paul]

DHCP is not properly configured.

In this case server is setting gateway for the whole network.

Properly configure DHCP on wireless devices.

[James Walton]

Could you elaborate please? I believe DHCP is configured correctly since wired clients receive an IP address without issue.

[josh000014]

Are you assigned vlans to each separate ssid or are they all on the same network? If you are using vlans, I would make sure the switchport the WAPs are connecting to are configured as trunk ports and tagging is working properly. 

[James Walton]

There is only one SSID and it uses the default VLAN (1) which matches the default VLAN on the switch.

I've just jumped on the switch and noticed an active dhcp pool, so I guess that must be interfering! Not sure what it's doing there, it's certainly not required.

I've tried to remove it by issuing the no ip dhcp pool command, which ran without error, but the pool is still present when I show run? If I try issue the no ip dhcp command again it says the pool is not in the database??

Excerpt from running config:

no ip dhcp use vrf connected
!
ip dhcp pool guest-builds
   default-router 192.168.69.254
!

When I try run the no ip dhcp pool command:

Switch1(config)#no ip dhcp pool guests-builds
% guests-builds is not in the database.

[josh000014]

Try running 

Switch>#clear ip dhcp pool guest-builds binding *

There may be some leases stuck in there. The syntax may also differ on your switch so use the ?.

I think without the network command in the dhcp pool it shouldn't hand out anymore addresses.

Hope this help!

Josh

[James Walton]

Turned out to be a typo in my command! I've managed to remove the pool now and will monitor to see if it resolves the original DHCP issue.

[James Walton]

This issue is still occurring unfortunately :( any more ideas anyone?

[josh000014]

Could you paste the switch config? Also are there any other switches on network? On the switch could you do

show vlan

show int trunk

and post.

Thanks!

Josh

[James Walton]

Hi Josh,

I'm back on site on Friday so I'll update this thread then. I also have an open Cisco support case, so hopefully I can get this resolved soon.

Cheers

James

[James Walton]

Sadly this issue is not resolved. I am on site today and could not get an IP address when trying to connect to the wireless network. This was affecting 2 of the 4 WAPs on the site. The one I normally have the issue with is working OK.

I then plugged directly in to the LAN but still couldn't get an IP address so I suspected a DHCP server issue or rogue DHCP server on the LAN. I stopped the DHCP service on my server and did not get an IP address, so I don't think there is a rogue.

I started the DHCP service and still couldn't get an IP address (wireless or wired). I then opened the DHCP console and noticed the server address was '169.254.x.x'! Never seen this before, so did a quick bit of research and this led me to disable all the NICs not in use on the server and restart the service again. This seemed to fix the issue and the server name came back up in DHCP instead of the 169 address.

I could then get IP addresses on the wired connection only.

I could not get IP addresses on wireless until I restarted (pulled the plug) the 2 WAPs.

Really puzzled with this one but it seems as though everything could be a knock-on effect of an issue with the DHCP server.

Anyone come across similar behaviour before? Although I don't suspect an issue with the switches, I will post the config here anyway (please see attachment). Maybe someone will spot something strange in there.

You will see the interface that the DHCP server and WAPs are connected to in the interface descriptions.

[josh000014]

I have seen this problem if there are multiple NICs on the server I would disable them if they aren't in use. You can also go into DHCP on the server and right-click on the hostname or IP address on the left pane and click add/remove bindings. Make sure only your desired IP address is checked.

Hope this helps!

Josh

[Eric Moyers]

My name Eric Moyers. I am an Engineer in the Small Business Support Center.

I am sorry to hear that you are experiencing this issue. 

First, you do not need a contract to get help with this device. They come with 1 year free phone support with proof of purchase. 

http://www.cisco.com/c/en/us/support/web/tsd-cisco-small-business-support-center-contacts.html

There are a couple of different possibilities that could be causing your issue. I would suggest calling in and opening a ticket. That would ensure the fastest response time to get this resolved.

Eric Moyers
.:|:.:|:. CISCO | Cisco Technical Support | Wireless and Surveillance Subject Matter Expert

Please rate helpful Posts and Let others know when your Question has been answered.

[James Walton]

Thanks Eric, I have successfully opened a case. I will report back with the solution once this is resolved.

[Eric Moyers]

What was your case number, I will keep tabs on it.

Eric