Cisco DHCP

Server

Exclude IP Addresses, Create DHCP Address Pool, Specify the Network, Set DNS Server, Set the Default Gateway

ip dhcp excluded-address [start ip-address] [end ip-address]
ip dhcp pool [poolname]
 network [ip-address] [subnet-mask]
 dns-server [ip-address of primary dns-server] [ip-address of secondary dns-server]
 default-router [ip-address]
exit

Client

interface Ethernet 1
 ip dhcp client hostname R1
 ip address dhcp

Renew

renew dhcp ethernet 3/1

Relay

interface Ethernet 1
 ip helper-address 10.0.0.10

Allows the DHCP relay agent to switch the gateway address (giaddr field of a DHCP packet) to secondary addresses when there is no DHCPOFFER message from a DHCP server.

ip dhcp smart-relay

Snooping

DHCP snooping is a DHCP security feature that provides network security by filtering untrusted DHCP messages and by building and maintaining a DHCP snooping binding database.

ip dhcp snooping
ip dhcp snooping vlan 10
ip dhcp snooping information option
interface gi1
ip dhcp snooping limit rate 100

Show

show ip dhcp snooping