The caching service in Mountain Lion Server (OS X Server 10.8) by default can use any interface installed on the system. I’ve now seen a couple instances where we have a Small Tree card and when a big update comes up, we loose file services speed due to caching data. To combat this, we can tell the Caching service to use the built-in Ethernet interface exclusively instead. To do so, first use ifconfig to determine which interface is which. Then tell the caching service which to use, using the serveradmin command, followed by settings and then the name of the setting, caching:Interface, setting the value to the en of the interface you’d like to use:
serveradmin settings caching:Interface = en1
I’ve had to restart the caching service to have this change take effect:
serveradmin stop caching
serveradmin start caching
Clients will then automatically use the correct interface.