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I am running a router on OpenWRT 15.05.1 and I did notice, that it does not send out Gratuitous ARP packets on a change of the IP address, nor on a reboot, nor on change of the Ethernet link state.

In the meanwhile I found out, that there is an option called arp_notify in /etc/sysctl.conf, but it does not work for some reaseon.

cat /proc/sys/net/ipv4/conf/br-lan/arp_notify returns 1 right now, so I guess it should be enabled, but it still does not send the Gratuitous ARP packet on one of the mentioned situations.

I also stopped the firewall with /etc/init.d/firewall stop to prevent any issues from there.

The command arping -A -I br-lan x.x.x.x sends it properly, so in general it is possible to create and send such a packet.

What is required to send out a Gratuitous ARP packet by the Linux kernel at an OpenWRT system on a change of the network settings, on a reboot or a link state change?

(I probably can find a scripted solution for it with the hotplug system, but I want to know why it does not work with arp_notify how I think it should)

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