Stop ARP responses for loopback adapters for loadbalancing.

If you are using a linux type loadbalancer, and have set up an additional interface say eth0 for your secondary loadbalanced IP, you will want to stop the interface from responding to ARP requests so that your switch only gets ARP requests from the loadbalancer and not your actual host.

To do this you need to put some entries in /etc/sysctl.conf as below – NOTE you will need to change the interfaces to suit your config.

net.ipv4.conf.lo.hidden = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.conf.eth0.arp_ignore = 1
net.ipv4.conf.eth0.arp_announce = 2
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2

Once these entries have been loaded in, either reboot or type

#sysctl -p /etc/sysctl.conf

Sorted, no more ARP conflicts.

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