5. Renewing lease

This is similar to the first DHCP REQUEST but with a crucial difference: the client knows its IP address and that of the server. As the DHCP server is on a different subnet, requests bear the MAC address of the router.

   UDP 163.1.15.99:68 (00:00:39:1C:0C:32) > 
       129.67.1.180:67 (00:D0:BC:00:11:22) DHCP REQUEST

   UDP 129.67.1.180:67 (00:D0:BC:00:11:22) > 
       163.1.15.99:68 (00:00:39:1C:0C:32) DHCP ACK
A DHCP NAK may be returned by the DHCP server if the lease cannot be renewed, at which point the client should abandon its IP address (and may send a DHCPDISCOVER).

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