Self-Assigned IP Address

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
I go out for coffee every morning. All of the venues I visit have WiFi Access Points. I have trouble with only one. At that one place both my iPhone and iPad always get a self-assigned IP address. Other customers, including those using Apple devices, seem to have no trouble at all. I have tried renewing the lease, forgetting the network and resetting the network settings. (I even did a factory reset of the iPhone for other reasons.) Nothing works.

The only way I can connect to the network is if I manually enter the IP address, subnet mask and router address. (I asked other customers about their IP address and worked out what I needed to enter manually.)

This place is one of a chain. They all use the same SSID and Password. I can connect fine at all the other venues. It's only this one where I have problems. The only clue is that they are using a ZTE modem at this place. The only other branch where I know the modem brand has a TP-Link.

Two questions:

  • Why me?
  • What can I do to fix this?


2019-08-15 10.53.59.png
 

throAU

macrumors 604
Feb 13, 2012
6,733
4,372
Perth, Western Australia
Maybe they are out of IP addresses on that DHCP scope (or their lease time is too long) and they need more (or shorter lease duration), and unfortunately you are connecting after the lease is fully used and thus lost out.

This is a network issue that their network administrator will need to diagnose and resolve, there is nothing you can do about it as a wireless client.
 
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Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
Maybe they are out of IP addresses on that DHCP scope (or their lease time is too long) and they need more (or shorter lease duration), and unfortunately you are connecting after the lease is fully used and thus lost out.

This is possible, but it doesn't explain why it always happens to me or why I never see anyone else having the same problem. It seems odd that every IP address has been assigned when I walk in the door, but somehow a lease expires just in time for the customer coming in after me. It's a smallish place so it's not difficult to watch people log in. In five or six years I've never seen another failure. And, I've never had a success. What are the odds?

I did a scan of the LAN. As you can
see, less than two dozen IP addresses have been assigned. At that time, there were only a few customers using the WiFi, plus three staff, their IP TV and Desktop which is in the back office.

2019-08-15 10.49.25.png
 

throAU

macrumors 604
Feb 13, 2012
6,733
4,372
Perth, Western Australia
This is possible, but it doesn't explain why it always happens to me or why I never see anyone else having the same problem.
Not knowing how many other people are there, and how short of IPs they are, i can't comment further.

However another option is that the network admin has explicitly told their DHCP server to blacklist your machine's MAC (hardware) address, in which case the path to resolution is the same: the network administrator needs to fix it.

Also - your network scan only shows currently connected machines - if the admin has done something like say, assign a 30 day lease, then there may be many IPs "in use" by machines that are not currently connected, but have been (and thus have consumed an IP from the pool) up to 30 days ago (as an example).

You also don't know how many IPs are in the assigned scope - maybe the whole subnet, maybe he/she only configured a handful (say, 192.168.1.32 - 192.168.1.50, or 192.168.1.60, etc.) for allocation. Maybe the "admin" is clueless (just equivalent of a home user who plugged it in and ran with defaults) and that brand of router only enables a small scope for allocation by default?

You need to talk to the network admin. This isn't something you can fix from your client. That may not be what you want to hear, but that's pretty much the situation you're in.



edit:
I say this as someone who does network administration as my day job since 1995.
 
Last edited:

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
However another option is that the network admin has explicitly told their DHCP server to blacklist your machine's MAC (hardware) address, in which case the path to resolution is the same: the network administrator needs to fix it.

This makes no sense. Why would they do that? I'm a long time, well known, frequent customer. I'm a "member" of their "club". (I get a discount. Wow!) My daughter works for the company. Why would they blacklist my MAC addresses at only one of their outlets?

Also - your network scan only shows currently connected machines - if the admin has done something like say, assign a 30 day lease, then there may be many IPs "in use" by machines that are not currently connected, but have been (and thus have consumed an IP from the pool) up to 30 days ago (as an example).
At the time I did the scan there were three customers, three employees, an IP TV and the desktop machine in the back office.

You also don't know how many IPs are in the assigned scope - maybe the whole subnet, maybe he/she only configured a handful (say, 192.168.1.32 - 192.168.1.50, or 192.168.1.60, etc.) for allocation.
As far as I can tell, the entire subnet is available. Over the years I've tried many IP addresses in that range. They all seem to work if they're not already in use.

I understand what you're saying about the entire subnet being allocated. But that doesn't really explain why people who come in after me are able to get an IP address but I am not. Am I really that unlucky to always walk in just as the entire subnet has been allocated. And, do other people walk in just in time for a lease expiration? Doesn't sound logical to me.

The chance of me talking to a network administrator are slim. For one, I don't speak Thai, so would have a horrible time explaining this.

So, I guess it will remain a mystery unsolved. At least I have a decent workaround.

Thanks for taking the time to respond.
 

adrianlondon

macrumors 68030
Nov 28, 2013
2,579
2,467
Switzerland
Did it ever work? I know some places keep track of the Mac address somehow and allocate the same IP address each time. It could be that since you first went, they've changed their IP address range but messed up that part of the automatic allocation. I've only known places do this where they require you to register (usually using your phone number to receive a texted password).

I can't think of any other reason off the top of my head. You've already done what I would have done (lease renew, forget network and rejoin).
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
Did it ever work?


If it did, it's been so many years that I don't remember. The only reason that it came up today is that I lost my note which contained the server IP address, so I had to ask another customer for their IP which enabled me to enter the correct data manually. (They were using a MacBook Air.)

Anyway, my workaround works. And, as @throAU said, I'm probably going to have to get with a network manager to figure out the problem. Maybe I can talk one of the employees into rebooting the router. (How do you say that in Thai
.)
 

adrianlondon

macrumors 68030
Nov 28, 2013
2,579
2,467
Switzerland
IT vocabulary is usually standardised on English. Having said that, the first time I heard an American ask about a router I couldn't understand what they were talking about.

Just when I was going to attempt to put some phonetic explanation as to the difference between BRitish and American pronunciation of the word "route", I realised that the word "row" has two pronunciations depending on context. " I'm having a row with my partner, because they wouldn't row the boat.". Maybe Thai is easier :)
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
OK, I just spoke to my daughter who worked at this branch for the first time this week. I asked her if any customers had trouble connecting to the WiFi. She said that a few did. But, there’s no consistency. Many come in and connect. A few come in and cannot.

I think @throAU is correct. It’s a lease problem. If you come in just after a lease has expired you’ll be OK. If you’re less lucky, like me, you’re gonna be SOL.

I told her I could fix it. We’ll see.
 

throAU

macrumors 604
Feb 13, 2012
6,733
4,372
Perth, Western Australia
Even if the lease is only say a few days - if they have a large number of customers (say, a hundred per day) who use the WIFI, their entire subnet will run out in 3 days, and a typical lease time out of the box is 3 days.

There may only be 5-10 people using the wifi while you're there, but a cafe will have a high turnover of people who spend maybe half an hour there at a time...

They should probably shorten the lease time down to 1-2 hours.
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
I've told my daughter what the problem is and offered my help. She's just starting out with this job, so she may not feel comfortable being that forward about it. We'll see.

Most of the traffic at this location is take-out. People on their way to Bangkok who stop in on their way out of Korat.

But, I suspect many of them use the WiFi for a few minutes while they're waiting for their beverage to be prepared.

2019-08-15 10.24.20.jpg
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
Update:

My daughter has now worked at this place a few more days. She says that no other customer has problems connecting to the WiFi. "Only you."

I wrote to their IT department about the lease length issue. They thanked me for the suggestion and said that they do not have problems with the WiFi.

I went there today and once again got self-assigned IP addresses on both my iPad and iPhone. I watched a guy with an iPad log in and connect immediately and another guy with a laptop I didn't recognize log in and get connected immediately.

So, apparently it's only me. How can that be?
 

throAU

macrumors 604
Feb 13, 2012
6,733
4,372
Perth, Western Australia
So, apparently it's only me. How can that be?
Could be an issue with reception where you sit?

A self assigned IP address happens when no DHCP response is received in a timely manner.

Given nobody else appears to have a problem the issue can only be either with
  • your device(s)
  • your software on your device(s) somehow
  • your behaviour (e.g., where you sit, etc.).

Try removing the wifi network from your devices (forget network) and adding it again in case there is something screwy in the profile.
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
Nope. I can see the router from where I sit.

If I manually configure the connection (IP address, Subnet Mask, Router IP, DNS Servers) I can connect just fine with a very strong signal. (I've kept a record of other customer's network configurations so I can pick a likely IP address for manual configuration.)

And, the guy with the iPhone this morning had a concrete wall between him and the router. I had line of sight.
 

throAU

macrumors 604
Feb 13, 2012
6,733
4,372
Perth, Western Australia
Nope. I can see the router from where I sit.

If I manually configure the connection (IP address, Subnet Mask, Router IP, DNS Servers) I can connect just fine with a very strong signal. (I've kept a record of other customer's network configurations so I can pick a likely IP address for manual configuration.)

And, the guy with the iPhone this morning had a concrete wall between him and the router. I had line of sight.
Well if the reception is ruled out, the only other thing is your device. Wipe the network from it and re-add. It's possible that the configuration for that wifi network is somehow borked on your device, and wifi profiles are synced among devices on the same icloud account. Thus, if it is syncing a borked profile, all your devices on the same icloud account will maybe be similarly borked.

So... remove, re-add.
 

Buadhai

macrumors 6502
Original poster
Jan 15, 2018
288
76
Korat, Thailand
I've done that many times to no avail. What I've tried:
  • Forgetting the network (countless times)
  • Resetting network settings (many times)
  • Factory reset (iPhone only 1 time)
This has been going on since 2015.

This photo was taken from where I usually sit in August of 2015. The router sits right next to the fridge.

2015-08-07 09.36.35.jpg


At this point I figure it's a problem that will never be solved. However, one additional factor:

This coffee shop has several branches. All of the branches use the same exact SSID and Password. I can connect just fine at other branches, it's only this one that fails. My daughter, who works at various branches, can connect to WiFi in all of them with her iPhone 7.
 
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