Each computer that uses the TCP/IP protocol suite needs to know four piece of information: The IP address of the computer The subnet mask of the computer The IP address of a router The IP address of a name server

1. Lecture
1

2.  Each computer that uses the TCP/IP protocol
suite needs to know four pieces of
information:
◦ The IP address of the computer
◦ The subnet mask of the computer
◦ The IP address of a router
◦ The IP address of a name server
2

3.  Reverse Address Resolution Protocol (RARP)
◦ RARP was designed to provide the IP address for a
booted computer.
◦ Not used for two reasons:
1. RARP used the broadcast service of the data
2. RARP can provide only the IP address of the
computer link layer.
 Bootstrap Protocol (BootP)
◦ BOOTP is the prerunner of DHCP.
◦ It is a client/server protocol designed to overcome
the two deficiencies of the RARP protocol.
◦ BOOTP, however, is a static configuration protocol
3

4.  What if:
◦ A host moves from one physical network to another
◦ A host wants a temporary IP address to be used
for a period of time
 BOOTP cannot handle these situations
because the binding between the physical
and IP addresses is static and fixed in a table
until changed by the administrator.
4

5.  DHCP is a client/server protocol designed to
provide the four pieces of information for a
diskless computer or a computer that is
booted for the first time.
 DHCP is a successor to BOOTP and is
backward compatible with it.
 The DHCP client and server can either be on
the same network or on different networks.
5

6. 6

7. 7

8. 8

9.  What if:
 A request is lost or damaged?
 What if the response is damaged?
 DHCP requires that UDP uses the checksum.
 The DHCP client uses timers and a
retransmission policy if it does not receive
the DHCP reply to a request.
9

10. 10

11.  DHCP can also be configured on a router…
 To configure a DHCP server for your hosts, you need
the following information at minimum:
 Network and mask for each LAN All addresses in a
subnet can be leased to hosts by default.
 Reserved/excluded addresses Reserved addresses for
printers, servers, routers, and so on. These addresses
will not be handed out to hosts. The first address of
each subnet is usually reserved for the router, but you
don’t have to do this.
 Default router This is the router’s address for each LAN.
 DNS address A list of DNS server addresses provided to
hosts so they can resolve names.

12. 1. Exclude the addresses you want to reserve. The
reason you do this step first is because as soon
as you set a network ID, the DHCP service will
start responding to client requests.
2. Create your pool for each LAN using a unique
name.
3. Choose the network ID and subnet mask for the
DHCP pool that the server will use to provide
addresses to hosts.
4. Add the address used for the default gateway of
the subnet.
5. Provide the DNS server address(es).
6. If you don’t want to use the default lease time of
24 hours, you need to set the lease time in days,
hours, and minutes

14.  Router(config)#ip dhcp excluded-address
192.168.10.1 192.168.10.10
 Router(config)#ip dhcp pool Sales_Wireless
 Router(dhcp-config)#network 192.168.10.0
255.255.255.0
 Router(dhcp-config)#default-router 192.168.10.1
 Router(dhcp-config)#dns-server 4.4.4.4
 Router(dhcp-config)#lease 3 12 15
 Router(config)#interface fa0/0
 Router(config-if)#ip helper-address 10.10.10.254