OS X Mavericks network timeouts

December 09, 2013

Initially when Mavericks hit the app store, i was eager to try it out, so started with upgrading my Mac mini from 10.8.5 to 10.9.

Installation was successful, and I started testing smb2 out, as this was the main reason for the upgrade, however i found that it was terrible slow – copying 1GB would take around an hour..

Started a ping towards different IP addresses on different vlans, and noticed that pinging when routing was needed would give me timeouts of 5 seconds every 30-45 seconds..

Found this thread on the apple forums: https://discussions.apple.com/thread/5483424?tstart=0

And this was exactly my problem, my network core consists of 2 Cisco Nexus 5548UP with some 2248’s connected, they are configured with vPC and HSRP, and in Mavericks arp is unicasted which causes mac addressed to flap between the 2 5548’s.

So the solution to the problem:

sudo sysctl -w net.link.ether.inet.arp_unicast_lim=0

or set it in the /etc/sysctl.conf

sudo sh -c 'echo "net.link.ether.inet.arp_unicast_lim=0" >> /private/etc/sysctl.conf'

which makes arp broadcasted and not unicasted.

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