Number of DHCP server lease limit on V2 ?
Is there a limit for the number of leases a DHCP server can hold simultaneously ?
Let's say on hardware like Alix 500Mhz with 256MB ram ?
What are the resources needed for the tables, including arp ?
Hard to say that with any exact numbers. The leases file can grow quite large with many leases (in /var/dhcpd/)
The arp tables don't take up much, but again the exact numbers are hard to say for that.
For the state table, 1 state is ~1KB of RAM, so with everything else on the ALIX you'd probably want to keep that under 100,000. If that much… more like 40-50,000 would probably be better, but that depends on what other things you have using RAM.