How to enable or disable Proxy ARP on Linux

Let’s look at the status of Proxy ARP (1 – enabled, 0 – disabled):

cat /proc/sys/net/ipv4/conf/all/proxy_arp

You can look at a specific network interface (where eth0 is the name of the network interface):

cat /proc/sys/net/ipv4/conf/eth0/proxy_arp

You can enable Proxy ARP as follows:

sudo su
echo 1 > /proc/sys/net/ipv4/conf/all/proxy_arp
echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp

Or so:

sudo sysctl net.ipv4.conf.all.proxy_arp=1
sudo sysctl net.ipv4.conf.eth0.proxy_arp=1
sudo sysctl -p

To turn off the Proxy ARP commands are similar, you only need to specify 0 instead of 1.

The above changes will be reset after restarting the system so that this does not happen, open the file /etc/sysctl.conf in any text editor:

sudo nano /etc/sysctl.conf

And specify:

net.ipv4.conf.all.proxy_arp=1
net.ipv4.conf.eth0.proxy_arp=1

If necessary, you can see the incoming ARP packets via tcpdump:

sudo tcpdump -n -i eth0 -e arp
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