Customer observations:

Troubleshooting network issues, we realized that the DHCP needs up to 5 DHCPDISCOVERs before actually handing out an IP. In the meantime it checks for available addresses and ignores the DISCOVER if the first IP it tests isn't available. See following excerpt from the dhcpd.log, and I'll attach the trace. Note that the trace differs 68 seconds from the log dates.

Please check the behavior and tell me if this is expected. I'd expect the DHCP to try IPs until it finds a working one, rather than trying one after another and wait for new DISCOVERs in the meantime.

The Idea:

"DHCP server to immediately continue running the ping-check against a next free IP address that it wants to offer if it has received an ICMP Echo reply with the ping-check against a previous free IP address that it wanted to offer, until it does not receive an ICMP Echo Reply and can actually offer the IP address per DHCPOFFER response, or until it has run an icmp-check against all free and abandoned IP addresses that it wanted to offer and found out that all these IP addresses are already in use or until a timeout has exceeded (I would suggest using the ping-timeout configuration for this purpose as well)."

/Stanimir Hristov