modem help

lgwjames · ‎01-11-2025

DHCP lease time (on your modem or router) is how long a device keeps the IP address it’s assigned before the router renews or reclaims it.

I’ve installed broadband and routers for about five years, so I know what DHCP lease time is. For some reason, Three has set it to one day.

The router menu says: “The setting can only be changed when the modem is disconnected.”

On most installs I did for Telewest, NTL, Virgin Media, and Sky, the lease time was set to about a month.

clivejo · ‎01-11-2025

Which DHCP lease are you talking about? On routers there are usually two, WAN side (internet) and LAN (local network)

WAN side IP's are assigned via the APN you are using, '3internet' is designed to assign a public IP (direct internet access) and three.co.uk assigns a private IP (access to internet is via Carrier Grade Network Address Translation (CG-NAT). You can check your access type using a NAT checker such as - https://natchecker.com

LAN side DHCP (which I assume you are talking about) is handed out by the router to devices on your local network and tend to be on the 192.168.x.x range. It sounds like you need to disable your WAN (turn off mobile data) to be able to change those settings. It's not unusual to see a lease time of a day, and should be perfectly fine in most home environments, is it causing you problems?

TBH it would cause me issues because I like to use static leases. There are certain devices on my network I want to be on certain IP's like printer, NAS, HomeAssistant instance etc

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clivejo · ‎01-11-2025

Which DHCP lease are you talking about? On routers there are usually two, WAN side (internet) and LAN (local network)

WAN side IP's are assigned via the APN you are using, '3internet' is designed to assign a public IP (direct internet access) and three.co.uk assigns a private IP (access to internet is via Carrier Grade Network Address Translation (CG-NAT). You can check your access type using a NAT checker such as - https://natchecker.com

LAN side DHCP (which I assume you are talking about) is handed out by the router to devices on your local network and tend to be on the 192.168.x.x range. It sounds like you need to disable your WAN (turn off mobile data) to be able to change those settings. It's not unusual to see a lease time of a day, and should be perfectly fine in most home environments, is it causing you problems?

TBH it would cause me issues because I like to use static leases. There are certain devices on my network I want to be on certain IP's like printer, NAS, HomeAssistant instance etc