Skip to main content

Different public IP depending on which device is connected to the internet? [Resolved]

I am wondering why my router has one public IP, and if disconnect the router and connect my laptop directly into the wall, I get another public IP, and if I connect my other laptop, I get yet another public IP.

I am using DHCP on all devices.

I tried releasing and renewing the DHCP lease, but I keep getting the same IP (3 different ones) on all devices.

I thought that my ISP would give the same IP to all my devices if they connect to the same outlet in the wall, but that does not seem to be the case. They do not seem to care either that I release and renew the lease.

Do they store the MAC adress connected and give that device a DHCP lease, and then keep that for however long they want? Or how do they know to give the same IP to my different devices every time? Is this normal practice by an ISP?

I took a couple of screenshots from 2 of my devices, to illustrate my point.

I searched on google, but found mostly posts about how someone's router's public IP differs from the public IP you find when you run curl https://ipinfo.io/ip for example, which is not the case here.

laptop1 pic1

laptop1 pic2

router pic1

router pic2


Question Credit: gstav
Question Reference
Asked June 12, 2019
Posted Under: Network
53 views
2 Answers

Short answer is that ISPs use DHCP to deliver IP addresses to the devices connected to their network. DHCP by default stores the MAC address along with the lease and uses the MAC address to ensure to the best of its ability that a regularly connecting device obtains the same address, therefore making what is in true nature a dynamic address what I like to call a "psuedo-static address"


credit: kelvintechie
Answered June 12, 2019

Few IPSs give you a static IP address unless you're explicitly paying for one. Usually you'll simply get an address from their DHCP pool based on the MAC address of the specific network interface you've connected to their network.

(https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol)


credit: Mikael H
Answered June 12, 2019
Your Answer