Don:
It depends on the nature of your network and the IP subnetting scheme you're using.
512 ARP entries for a VLAN would imply that you were setting up an IP subnet that is /23, which would give you 512 host addresses. That's not something I would normally recommend unless there were very specific circumstances that required that large of a broadcast domain.
Most customers use a standard /24 or even smaller subnets, so the ARP cache limit of 512 isn't an issue.
Regards,
Ronnie Colvin
Adtran Applications Engineering
