DHCP commonly used four kinds of messages based on UDP67 server, 68 port client
discover broadcast
offer unicast
rquest broadcast
ack unicast
When DHCP 50% of the time renews the lease, the request message is a unicast message.
When DHCP 87.5% of the time requests to rebind the IP, the request message is a broadcast message.
Alternative configuration scheme of DHCP:
load balancing:
ip relay address cycle first enable relay load balancing globally
interface vlan10
ip add 192.168.1.1 24
dhcp select relay
dhcp relay server-ip 10.1.1.1
dhcp relay server-ip 10.1.1.2 Specify two DHCP server relay load balancing