Super Quick Setup for a Temporary Linux Router

I often need to quickly setup a router using my linux laptop and hence documenting the general steps.

Lets assume wlan0 is the internet facing interface while eth0 is the LAN interface.

Add/Edit the following in /etc/sysctl.conf

net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1

Execute the following command to setup the sysctl values.

sudo sysctl -p /etc/sysctl.conf

Make sure the default route is pointing to wlan0

Masquerade on the internet facing interface i.e. wlan0

sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE

Now give eth0 an IP and use an IP in the same broadcast range as eth0 for the device sitting on the LAN.

For eg

sudo ifconfig eth0

And now use for the device on the LAN network.

Additional step could be to setup a dhcpd server on the eth0 interface. Here’s a sample dhcpd configuration

default-lease-time 600;
max-lease-time 7200;
subnet netmask {

Now to run the dhcpd server on eth0

sudo dhcpd -f -cf /etc/dhcpd.conf eth0

Remove the -f if you want to run dhcpd in background.

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