The default time that ARP entries are cached in a Sun Solaris system is 5 mins.
However, this can be reduced to lower level (say 3mins). This means that the number of ARP requests and ARP replies to and from the server will increase as a result. So, before modifying the caching time, check if this can cause andy congestion on your network.
To set the ARP cache time period
solaris# ndd -set /dev/arp arp_cleanup_interval 180000
The above command sets the interval to 3 minutes (1min is equal to 60000ms). Now, all the ARP entries are flushed at a faster rate (every 3mins)
For this change to persist across reboots, add this command onto the init scripts in /etc/rc2.d directory for your network interface (where all the required ndd commands are run).