otl , 7 months ago

Time to turn your laptop into a router! Let’s say you’ve got 2 network interfaces on your laptop, eth0 and wifi0. wifi0 is joined to your university WiFi as normal. Connect your iPad to your laptop via ethernet (with a USB-C adapter).

<span style="color:#323232;">iPad -> usb-c-ethernet -> eth0
</span><span style="color:#323232;">wifi0 -> internet
</span>

Rather than setting up a DHCP server or IPv6 stuff, I’d just configure the wired interfaces manually. Let’s use the network 192.168.69.0/24. Laptop will be 192.168.69.1, iPad will be at 192.168.69.2. On the laptop:

<span style="color:#323232;">ip addr add 192.168.69.1/24 dev eth0
</span>

On your iPad, go to Settings -> Ethernet:

• address: 192.168.69.2
• subnet mask: 255.255.255.0
• router: 192.168.69.1

Curious to see if that works. We haven’t set up DNS or DHCP or done any sysctl for IP forwarding or any nftables.

How can we test if it works? We can set up a TCP listener using nc(1) on the laptop that the iPad’s web browser could hit. On the laptop:

<span style="color:#323232;">nc -l 8080
</span>

On your iPad, open Safari and browse to 192.168.69.1:8080

Curious to see if that all works!

---

See also:

• man.openbsd.org/nc
• man7.org/linux/man-pages/man8/ip.8.html