3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 9 DHCP Configuration3Com Corporation9-5DHCPOFFER/DiscardDHCPNAK/Discard offerSELECTINGSelect offer/send DHCPREQUESTRENEWINGREBINDINGDHCPNAK,Lease expired/Halt networkDHCPNAK/Halt networkT2 expires/BroadcastDHCPREQUESTT1 expires/Send DHCPREQUESTto leasing serverDHCPACK/Record lease, settimers T1, T2DHCPACK/Record lease, settimers T1,T2INITBOUNDREQUESTINGDHCPACK/Record lease, settimers T1, T2DHCPACK(not accept.)/Send DECLINE-/Send DHCPDISCOVERDHCPOFFER/CollectrepliesDHCPOFFER,DHCPACK,DHCPNAK/DiscardFigure 9-2 DHCP client state transit9.2.3 Introduction to DHCP AccountingDHCP accounting enables a DHCP server to notify the RADIUS server of the start orend of accounting when assigning or reclaiming a lease. The cooperation of the DHCPserver and RADIUS server implements the network accounting function, and at thesame time improves the network security to a certain degree.I. Structure of the DHCP accounting packetThe interactive operations between the DHCP server and the RADIUS server arebased on two types of packets: accounting start request and accounting stop request.The two types of packets have the similar structure, and the only difference lies in theAttributes field. The following figure illustrates the packet structure:
