How do you disable and re-enable the DHCP (Dynamic Host Configuration Protocol) service on a Cisco router?

Use no service dhcp to disable and service dhcp to re-enable. The DHCP service is enabled by default.

R1(config)# no service dhcp    ! Disable DHCP server
R1(config)# service dhcp       ! Re-enable DHCP server

Key points:

• The DHCPv4 service is enabled by default on Cisco IOS routers
• Disabling the service only stops DHCP from responding — it does not delete your pool configuration
• Re-enabling the service reactivates DHCP with the existing configuration

Warning: Clearing DHCP bindings or stopping/restarting the DHCP service may cause duplicate IP (Internet Protocol) addresses to be temporarily assigned on the network. The server loses track of which IPs are in use, and might assign an address that a client still holds from a previous lease.