Rapid drain mode for DHCP address pools and lease timer enhancements

You can configure the DHCP local server to stop allocating addresses from a local pool and gracefully terminate subscribers that are using addresses from that pool. When a DHCP subscriber attempts to renew the IP address from a pool configured for active drain, the DHCP local server replies with a NAK to the subscriber's T1 renewal messages, forcing a renegotiation, at which time the server allocates a new IP address from an alternative address pool that is not configured for active drain. Also, you can now configure the duration for T1 (renewal) and T2 (rebinding) timers for inet and inet6 in seconds. In earlier releases, you can configure the duration of these timers only as percentages. You must use either seconds or percentages for both T1 and T2 for a given pool and address family; you cannot mix the units.