How are PCs updating their timezime, without having any local network access?

Posted by Fluffer_Wuffer@reddit | sysadmin | View on Reddit | 23 comments

Hi All This is something unusual - How are PCs updating their timezime, without having any local network access? For context - Myself and the wife myself and the wife are on holiday in Spain - unfortunately I have to carry work with me, which includes a couple of laptops (a Mac and a Lenovo laptop), and a travel router that tunnels everything back to the UK across via IPSec. Yet, both the Macbook and Lenovo have updated timezone to the Spain, without having any local network access... I suspect the answer is related to scanning local WIFI networks. Thanks

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23 Comments

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VA_Network_Nerd@reddit

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skreak@reddit

Your travel router has to get an IP over DHCP from whatever it's plugged into. DHCP can inform about time zone. So the router gets set. Then it is a DHCP server for your devices and it down streams that information. Also. Some laptops do have GPS devices in them that Windows can use as well.

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riffic@reddit

dhcp does not have anything to do with time

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Fluffer_Wuffer@reddit (OP)

Ahh OK, this could be something, ill check into it... the travel router is sat behind the hotel router, so WAN is on a 192 address.

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skreak@reddit

Doesn't matter if it's public or not. DHCP can give out way more than IP addresses. It can do dns, domains, hostnames, ntp servers, time zone, and much more. https://efficientip.com/glossary/dhcp-option/#:~:text=DHCP%20option%20100%3A%20time%20zone,suffixes%20provided%20in%20this%20list.

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pantherghast@reddit

They might be doing it through the SSID's of WiFi in your area even if you are not connected to them. Google collects SSID's while they collect information for Google maps. If you have a specific list of SSID and signal strength that match a geolocation, it is most likely you are there.

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Fluffer_Wuffer@reddit (OP)

This is what I'm thinking at the moment.

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edmunek@reddit

would your connection (on your laptops) completely drop if your router would temporarily lose the VPN tunnel? that could be the answer. Apart from that, I usually see that when I go abroad and remain (even on 3G) on a full tunnel back to UK, none of my services are aware that I am somewhere different (region-wise).

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Fluffer_Wuffer@reddit (OP)

Good question, I'll test this. But the IPSec has been up for days.. Its not an issue, but my wife saw this happen to her laptop a few months ago, and it's bugged me ever since, i work in IT, and like many of us, I don't like laptops doing shit I don't know about... unfortunately, it's a huge company, and end-point management is outsourced, so I've got no contacts there.

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OsmiumBalloon@reddit

Your computer still gets an IP address on the local network, and still has access to your local network connection. That's how your VPN client connects to your VPN gateway, after all. The OS services can still make use of that. So they geolocate on that and decide you're in Spain.

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CatoDomine@reddit

OP said his router is handling the VPN. The router is what gets the "local network" connection, not the laptops. Unless the router is configured to allow split tunneling, all of the laptop traffic should be going to the UK and the packets mangled on the UK side before going out to the internet.

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Fluffer_Wuffer@reddit (OP)

Exactly this... nothing touches the LAN in Spain.

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jmbpiano@reddit

> Your computer still gets an IP address on the local network They would if OP was running a VPN on their laptop, but they're not. OP is using > a travel router Only the router needs a local IP. A laptop hooked up to a properly configured router shouldn't be able to see anything but the VPN tunnel's traffic.

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lost_in_life_34@reddit

You still need a local IP

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Fluffer_Wuffer@reddit (OP)

The travel router WAN IP is on a 192 range, but the only thing leaving it, at least from a client perspective, should be the IPSec..

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CatoDomine@reddit

Yes and no. OP stated that they are using "*a travel router that tunnels everything back to the UK across via IPSec*". The router would certainly need an IP that is local - but the laptops do not.

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lost_in_life_34@reddit

it's still going to pick up a local IP and will have a local network for the PC to connect to  router gets local public IP and will have a local private network like any wifi router

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CatoDomine@reddit

The fact that the router is serving RFC 1918 "local IPs" is not relevant to OP's question in the slightest.

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OsmiumBalloon@reddit

I'm not sure why you're getting downvoted, you're dead on right.

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bofh2023@reddit

Indeed. I'm assuming Microsoft eats their own dogfood here so they probably use the windows location API of which there is [a high-level description here:]( https://learn.microsoft.com/en-us/uwp/api/windows.devices.geolocation?view=winrt-22621)

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mhkohne@reddit

The VPN runs across the local network. While the VPN will route everything over it once up, prior to that things will still be able to get to the local net.

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explodingtvroom@reddit

they're connected to something. might be worth trying to figure out what that is.

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Bllago@reddit

I'm not sure about Mac's, but Windows will update it's timezone in a multitude of ways. If you're connected through the VPN it will grab info still, usually before the VPN fully connects. Anytime Windows update service connects to Microsoft servers it will update, if you turned your computer on and your computer discovered open wifi it can update. The details of exactly what happened are the most important to determine exact reasoning, which you are unlikely to follow know since you weren't paying full attention (and why would you be?)