Validating the IP Address and Lease Negotiation

The following steps describe the IP address validation and lease negotiation process.
  1. At bootup, the device automatically checks its configuration for an IP address.
  2. If the device does not have a static IP address, it requests the lease of an address from the DHCP server:
    • If the server responds, it leases an IP address to the device for the specified lease period.
    • If the server does not respond (after four tries), the DHCP client process is ended.
  3. If the device has a dynamic address, the device asks the DHCP server to validate that address. If the server does not respond, the device continues to use the existing address until the lease expires. If the server responds, and the IP address is outside of the DHCP address pool or has been leased to another device, it is automatically rejected, and the device receives a new IP address from the server. If the existing address is valid, the lease continues.
    Note: The lease time interval is configured on the DHCP server, not on the client device. The ip dhcp-client lease command is set by the system, and is non-operational to a user.
  4. If the existing address is static, the device keeps it and the DHCP client process is ended.
  5. For a leased IP address, when the lease interval reaches the renewal point, the device requests a renewal from the DHCP server:
    • If the device is able to contact the DHCP server at the renewal point in the lease, the DHCP server extends the lease. This process can continue indefinitely.
    • If the device is unable to reach the DHCP server after four attempts, it continues to use the existing IP address until the lease expires. When the lease expires, the dynamic IP address is removed and the device contacts the DHCP server for a new address.
Parent topic: Configuration Notes and Feature Limitations for DHCP Auto-Provisioning