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DHCP randomly stops giving IP's to wireless devices - APIPA


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#1 David Ashcroft

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Posted 04 December 2013 - 07:37 PM

Hi, before anyone asks I have tried using several different routers from BT to resolve this issue with no luck.

Ill try to paint a picture first!

We have our main Router provided by BT (Business Hub 3). The hub is connected to a switch, the switch goes out to all wired devices on the network.

The switch has a couple of wireless access points plugged into it as we have a large site, the access points across the site (including the main router) all have different channels selected and only just overlap each other. When everything works devices seem pretty good at switching from one AP to another if one goes out of range. All AP's have the same SSID, password and security type etc so roaming seems to work (when it works! )

DHCP is disabled on all AP's and the BT router, we used Windows Server 2008 R2 running DHCP and DNS services.

Everything seems fine but when people come for lunch after roaming around the site, some may and some may not have internet access, all wireless devices such as iPads and phones, wired devices never have an issue!

After insepcting the devices they seem to end up with a 169 address and i have no idea why!
Sometimes when the router is switched off and on again it starts working again which i find even more strange since DHCP is not in use on it.

I have gone onto Windows Server and looked at the DHCP logs, and it seems a lot of people are having their leases renewed every few seconds, not sure if this is normal, or what could be causing it. DHCP leases are set to 8 days on the server.

A small portion of the DHCP log is below, you can see what it is doing sometimes.

Please help!

11,12/03/13,12:30:21,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,1904021297,0,,,
11,12/03/13,12:30:23,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,1904021297,0,,,
11,12/03/13,12:30:55,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,3738532478,0,,,
11,12/03/13,12:30:58,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,3738532478,0,,,
24,12/03/13,12:41:45,Database Cleanup Begin,,,,,0,6,,,
25,12/03/13,12:41:45,0 leases expired and 0 leases deleted,,,,,0,6,,,
25,12/03/13,12:41:45,0 leases expired and 0 leases deleted,,,,,0,6,,,
11,12/03/13,13:20:13,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1928272809,0,,,
11,12/03/13,13:20:14,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1928272809,0,,,
11,12/03/13,13:20:17,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1928272809,0,,,
11,12/03/13,13:22:07,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1961827241,0,,,
11,12/03/13,13:22:08,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1961827241,0,,,
11,12/03/13,13:22:11,Renew,192.168.1.101,Mattys-iphone.woodlands.farm,78CA398EBABD,,1961827241,0,,,
11,12/03/13,13:26:28,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,560813771,0,,,
11,12/03/13,13:26:30,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,560813771,0,,,
11,12/03/13,13:27:02,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,528184842,0,,,
11,12/03/13,13:27:05,Renew,192.168.1.116,android-5034be9390f051be.woodlands.farm,6CB7F460237C,,528184842,0,,,
11,12/03/13,13:27:31,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1148184775,0,,,
11,12/03/13,13:27:33,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1148184775,0,,,
12,12/03/13,13:32:34,Release,192.168.1.106,,888717A9F08A,,3870922839,0,,,
10,12/03/13,13:32:38,Assign,192.168.1.106,,888717A9F08A,,3870932902,0,,,
24,12/03/13,13:41:46,Database Cleanup Begin,,,,,0,6,,,
25,12/03/13,13:41:46,0 leases expired and 0 leases deleted,,,,,0,6,,,
25,12/03/13,13:41:46,0 leases expired and 0 leases deleted,,,,,0,6,,,
12,12/03/13,13:42:39,Release,192.168.1.106,,888717A9F08A,,3870932902,0,,,
10,12/03/13,13:42:41,Assign,192.168.1.106,,888717A9F08A,,3870964754,0,,,
11,12/03/13,14:05:48,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1181739207,0,,,
11,12/03/13,14:05:50,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1181739207,0,,,
11,12/03/13,14:05:52,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1181739207,0,,,
11,12/03/13,14:28:35,Renew,192.168.1.117,Bobette.woodlands.farm,30F7C58ADD71,,1215293639,0,,,
11,12/03/13,14:38:01,Renew,192.168.1.105,,183F47B7B176,,1909203724,0,,,

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#2 cryptodan

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Posted 04 December 2013 - 07:44 PM

I would start off by disabling DHCP on the BT Router so you are not running 2 DHCP Servers.

#3 David Ashcroft

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Posted 04 December 2013 - 07:52 PM

The post above says DHCP is disabled on the router and AP's :)

#4 cryptodan

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Posted 04 December 2013 - 08:50 PM

Oh sorry read that BT as but and BT lol.

Whats the release time show on Windows machines using

ipconfig /all

#5 CaveDweller2

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Posted 04 December 2013 - 09:07 PM

From what I am reading there it looks like there might be an issue with your wireless design. I say this because devices are getting the 169 address. They only get that if a DHCP server can not be reached. So they are getting disconnected and/or they are moving from 1 AP coverage to another and when their devices try to reconnect and/or switch to the new AP it's not getting a response. Restarting the APs would solve it cause it would send out a signal letting devices know it's there. You say they just overlap, the standard overlap should be 15%.

 

Can you manually reconnect them or do you have to restart the AP?


Hope this helps thumbup.gif

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#6 David Ashcroft

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Posted 05 December 2013 - 03:51 AM

Just come into the office this morning and walked straight to the location where it will pick up the main access point that people use (the one that people complain about things not working at lunch.

 

I checked my phone and had a APIPA address. 

 

I walked to another location where and my phone switched to another AP and connected instantly with no issues with a correct IP address.

 

Now i can roam and still have the correct address anywhere.

 

The main AP having the issues has been changed, i have tried 2 BT routers and also a Cisco router, all having the same issue so i am not convinced it is the router, maybe the way the router is setup?

 

Thanks! 

 

EDIT - Just checked the wireless on a iPad that has been left here overnight (near the main router) and it wasnt connected :( Again 169. address. this time i restarted the main router and everything works again!! So strange! 


Edited by David Ashcroft, 05 December 2013 - 04:21 AM.


#7 CaveDweller2

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Posted 05 December 2013 - 11:11 AM

I'm a little confused about your setup. Can you describe it from where the ISP comes into your site?


Hope this helps thumbup.gif

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#8 JohnnyJammer

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Posted 05 December 2013 - 08:37 PM

There is no mention of subnets or vlans either, if its a larger network i wouldnt be runnign that many hosts on 1 subnet. broadcast packets would be floodign that network, so i would be using vlans for wirelss traffic and have that point to the dhcp server, alsos et the dhcp lease time to 8 days (Default from memory).



#9 technonymous

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Posted 05 December 2013 - 11:48 PM

Seamless wifi roaming doesn't always work like you expect it to. Causes such as Hardware variations one router may be more robust with cpu/ram power and another not, sticky dhcp release/renew both server/clients, lease times on routers, channels, general interference, rogue AP's and VM's. Any wifi AP to AP bridging can just generally buggy. Probably best to just stick to POE AP's acting as their own networks with different IP ranges. For instance...network 1 (192.168.1.100) network 2 (192.168.2.100) and so on. You see a lot of these hanging from the ceilings in hospitals...http://www.newegg.com/Product/Product.aspx?Item=9SIA1EA0Y35726 Seamless everything needs to match, Key's, channel, ssid, but any hiccup along the way you got problems or some kind of a collision.


Edited by technonymous, 06 December 2013 - 12:06 AM.


#10 David Ashcroft

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Posted 06 December 2013 - 09:34 AM

Sorry I think i have made things seem bigger than they are! 

 

The internet comes into the site via a phone line (ADSL). Connected to the phone line is an ADSL Router.

 

Building 1 is a small office (where the phone line comes in and where the main ADSL router is connected). The office has about 6 computers.

 

Building 2 is a small pet shop, has 2 computers.

 

Building 3 just has IP cameras in it.

 

All buildings are only a few feet apart. Each building has its own Gigabit switch, Each building has its own access point. Each access point has little or no overlapping in terms of signal, all have same SSID and authentication type and password. 

 

Each building is linked simply via CAT5e cable. 

 

ALL physically wired devices work perfectly with no issues on DHCP, its just wireless devices.

 

There are no more than 30 devices on the network in total including AP's, router, cameras, computers, laptops, phones, servers etc.

 

Hope that builds more of a picture! :)



#11 cryptodan

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Posted 06 December 2013 - 09:41 AM

Can you please provide the lease information that is available from doing

ipconfig /all on a windows machine and provide that.

#12 David Ashcroft

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Posted 06 December 2013 - 10:00 AM

2 images attached, one with lease information from command prompt. Other images is recent log from DHCP showing something called NACK a lot, anyone know what this would be?

 

Our scope for DHCP is 192.168.1.100 to 192.168.1.250 (we use 192.168.1.1 to 192.168.1.99 for static and reservations). Subnets are all set to 255.255.255.0 however that NACK thing is 192.168.0.# and i have no idea what it is! 

 

Thanks again

 

 

 

Attached Files



#13 cryptodan

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Posted 06 December 2013 - 10:02 AM

Now can you show me the lease time on a wireless device?

#14 David Ashcroft

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Posted 06 December 2013 - 10:26 AM

Is it possible to do this on a phone? Iphone for example, its mostly phones having the issue :)

 

Thannks! 

 

Technically, they should be the same :)



#15 cryptodan

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Posted 06 December 2013 - 10:41 AM

I am not sure about that I am trying to see if there is a different lease time for wireless clients as opposed to wired.




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