iPad getting wrong IP address from router?

I have my router's DHCP server set to hand out static IPs based on a machine's MAC address, though keep my clients configured to grab their IPs with DHCP. I have some customized DNS and domain settings I like to propagate without manually configuring any machine that may join my network. The iPad plays well with this configuration most of the time, but it fails often enough to be annoying. When I manually assign the iPad an IP rather than fetch it via DHCP everything is seamless. My network has a wireless repeater on it to expand my range a bit, and I suspect this is what's occasionally causing the problem.

i've typed the password correctly

and every thing is ok

it's just from the ip

some times i get the dhcp blank

and some times 169

should i do anything ?

Yep, that did it!

I was about to get realy upset with this issue, finding all kinds of bogous explanations...

We actually had a hint testung a wifi cctv camera that Gould not work on some of the older routers, but on Brand New ones and very old ones it would!

thanks for the confirmation!

Thanks Golfboy, you solved my issue also. Same thing. Darn 11 g/b whatever that is, was giving me lots of grief!

I have had this problem too, but everything worked for weeks before it went wrong. I have just checked my router and discovered that I had reserved an IP address for an old printer which is now being used by a new printer using a fixed IP address. Possibly this was slowing the DHCP down and causing the problem described in another post. I deleted the reservation and the iPad picked up an IP address immediately. However this does not account for the weeks of normal operation.

My iphone was continually getting the wrong wifi ip address, I forgot the network, did the network reset and nothing worked! Then I simply switched off and unplugged the router, waited 10 secs, plugged it back in and switched on and the problem was solved!! Much to my relief!

Thank you Golf Boy!!

My iPad2 had connected to Netgear router with no problems for 2 years before suddenly picking up wrong ip address as above. Spent a whole day trawling for solutions, tried all sorts, close to giving-up as read over and over it's a router problem / iOS 6 not compatible with older router software, Golf Boy's solution of setting router to broadcast 11/b only finally did the trick! Changed the setting, told iPad to 'forget this network', unplugged router for a while, plugged it back in, logged into wifi, working at last.

This post is old but it popped up on the first page of my google search for this problem so I'm going to reply anyway.

My router has a setting where it can reserve an IP address for individual MAC addresses so that each time a device connects to the network, it's given the same IP. Well after a couple years, all the availible IP's had gotten reserved and there were none left for my new phone. Deleting some of the unused entries and now my phone connects as should.

Just another thing to check.

I have the same on an iPhone. I am using Unifi APs, and FireBrick DHCP.

I have narrowed the problem down to when the phone changes between APs (same SSID and network). It drops the existing DHCP lease regardless of lease or renewal time. It is a bit intermittent, but seems reasonably reproducible now.

The pcaps I have run show that it does not send a new DHCP request at all. In some cases I have seen it send one minutes later. During the gap it is actually working on IPv6 but not IPv4. Typically it will show no IPv4 on the WiFi status page, and eventually switch to a 169 address (which you use when no DHCP server).

I have seen LLC "receiver not ready" messages even. I have tried numerous changes to DHCP, including lease time, TTL on replies, and so on, but as it seems not to be sending a request at all during this period then there is nothing the DHCP server can actually do. It has been like this for quite some time, and is very annoying. I see if every day as I move through my house and it changes APs.

In all cases, turning wifi off and on, or turning airplane mode on and off, will immediately cause a DHCP request and correct allocation of IPv4.

I am happy to do more packet dumps if that would help Apple fix this.

It is more likely that the network is dropping the lease, not the phone. As the phone doesn't know it has been dropped it doesn't send a new DHCP request. I use my phone in offices with dozens of access points, and the connection moves from one to another seamlessly. Likewise for my ISP's public access points. There are something over 100,000 of them, and the phone always connects to the nearest one (even when I don't want it to).

No, this is the phone dropping it as in it shows no IP address on the wifi status page and does not answer the IP, either IP packets, or later ARPs, sent to it during this period. The phone has linked to the new AP and is using the same MAC as can be seen by working IPv6 traffic both ways during the period. The phone has dropped the IPv4 address on change of AP. There may be some other factor - make of AP, or use of IPv6 or something, but this is very repeatable.