Failover on six /18 "subnets"?

[Simon Hobson]

"Nicolas C." wrote:
>We are about to manage six /18 "subnets" in DHCP-failover mode. Is 
>anyone have feedback on failover for large networks?
>
>I'm a little worried by the time DHCP will need to initialize the leases 
>database and I don't want these large ranges to interfere with our 
>smaller subnets already in place.

This is governed by the size of the pools, not the size of the subnets - the server builds a hashed table with an entry for every possible lease it can offer. If your pools are the full /18 subnets, then I make that around 100k addresses to keep track of - and there have been reports of slow startup times when you get to this sort of scale. You wil need a fair bit of memory, and fast disks to manage that - you'll also need to address other factors, such as ensuring that logs are configured as asynchronous.