3Com 3C13636 Configuration Manual page 451

3Com Router 3000 Ethernet Family
Configuration Guide
Upon the receipt of the DHCP_Request packet, the DHCP server sends back a
DHCP_ACK packet allowing the client to use the requested address if it is still
unallocated.
If the DHCP server has allocated that IP address to some other DHCP client or it is
not available to the client for other reasons, the DHCP server sends back a
DHCP_NAK packet. Upon the receipt of the packet, the client may send a new
DHCP_Discover packet requesting a new IP address.
3) Renew the IP address lease
DHCP server takes back the dynamic IP address allocated to DHCP client when the
lease expires. If DHCP client still wants to use this address, it should renew the IP
address lease.
In practice, when the DHCP client starts or is at the half of the lease limit, it can send a
DHCP_Request packet to DHCP server to complete lease renewal. If the current IP
address is still valid, DHCP server returns DHCP_ACK packet to notify DHCP client
that it has renewed the IP address lease.
4) Configure PC
Use the ipconfig/release command under DOS environment or run [winipcfg/release]
at GUI (graphic user interface) to release an existing IP address. Then the user PC
sends DHCP_Release packet to DHCP server. Use the ipconfig /renew command
under DOS environment or run [winipcfg/renew] at GUI to request for new IP address.
Now the user PC sends the DHCP_Discover packet to DHCP server.
You can also use the ipconfig/renew command on the user PC or run [winipcfg /renew]
at GUI to renew the IP address lease.
The following figure presents the procedures described above:
3Com Corporation
9-4
Chapter 9 DHCP Configuration