fixMavericksUnicastIssue

#!/bin/bash

# Mavericks has a nasty issue regarding ARPs in corporate networks.
# It appears that they have tried to reduce bandwidth utilization by caching
# the results of ARPs. Unfortunately, this causes big problems with corporate
# networks with Virtual IPs or other corporate network redundancy measures.

# There exist other patches for this issue
# (see https://github.com/MacMiniVault/Mac-Scripts/blob/master/unicastarp/unicastarp-README.md)
# but they write a value that will be pulled everytime the machine reboots. Because
# we are assuming Apple will fix this in a future Mavericks update, we don't want this
# setting to last after a reboot. This script writes the fix, but it doesn't persist past a reboot.

# Author: Ben Limmer | [email protected]

if [[ "$(sw_vers -productVersion)" =~ 10\.9 ]]; then
  if [[ "$(sysctl -n net.link.ether.inet.arp_unicast_lim)" == "0" ]]; then
    echo "System is already properly configured."
    exit 1
  else
    echo "Your system is caching ARP updates."
    sudo sysctl -w net.link.ether.inet.arp_unicast_lim=0
    echo "Fixed ARP issue"
    exit 0
  fi
else
  echo "This patch does not apply to your operating system."
  exit 1
fi