Copyright © 2006 Heathkit Company, Inc. All Rights Reserved Introduction to Networking Technologies Dynamic Host Configuration Protocol (DHCP)

2 Default Gateway Default Gateway Subnet Mask Subnet Mask IP Address

3 Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP)

4 Dynamic vs. Static IP Addresses Static IP Address – Never changes. Dynamic IP Address – The server assigns an IP address each time a client logs on to the network.

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6 Dynamic Host Configuration Protocol (DHCP) Implemented in the Server. Hands out IP addresses as needed. Keeps track of which IP addresses are being used. Returns addresses to the pool when no longer in use.

7 The DHCP server provides: IP Address Subnet Mask Default Gateway Address DNS Server Address WINS Server Address Optional

8 DHCP Server Requirements: A static IP address, subnet mask, and other TCP/IP parameters. That is, the DHCP server can not provide its own TCP/IP parameters. The DHCP Service must be installed. The TCP/IP parameters to be doled out must be specified. This is called the scope. Once created the scope must also be activated. Finally, it must be authorized to act as the DHCP server.

9 The DHCP Process When a client boots-up, it broadcasts a request for an IP address from the DHCP server. The DHCP server responds with a broadcast of the offer of an IP address and subnet mask.

10 The DHCP Process (Continued) The client receives the offer and responds with a message saying: “Yes, sign me up for that one.” The DHCP server responds with a message saying: “Okay, you got it.” It also includes any additional TCP/IP configuration information such as Default Gateway, DNS address, WINS server address, etc.

11 The DHCP Lease The allocation of TCP/IP parameters is called a lease. The length of the lease is set in the scope. Leases periodically expire and must be renewed. Clients automatically attempt to renew their leases well before the lease expires.

12 Renewing and Releasing the Lease Use the IPCONFIG command IPCONFIG is a TCP/IP utility that is executed from the command line prompt. IPCONFIG /RENEW IPCONFIG /RELEASE

13 Segment 1 Router Segment 2 DHCP Server DHCP Server

14 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server

15 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server 1 1

16 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server 2 2

17 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server 3

18 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server 4 4

19 Segment 1 Router with DHCP forwarding Segment 2 DHCP Server

20 Segment 1 Router WITHOUT DHCP forwarding Segment 2 DHCP Server Configured for DHCP Relay Agent Configured for DHCP Relay Agent

21 When the DHCP server is on another subnet, configure: DHCP broadcast forwarding on the router. DHCP Relay Agent on the Server. OR

22 BOOTP Short for Bootstrap Protocol Allows diskless workstations to boot and obtain their required IP addressing information from a BOOTP server. The BOOTP server maintains a list of host’s MAC addresses and corresponding IP address information. The BOOTP server distributes the IP addresses as the hosts boot-up.

23 Both DHCP and BOOTP: Use UDP as their communications transport. Clients transmit address requests from their port 68. Servers receive the requests on port 67. Blocking ports 68 on clients or 67 on the server will defeat DHCP or BOOTP.

24 Now, it’s your turn.