CCNA 2 Chapter 8: DHCP
Introducing DHCPv4 - correct answer ✔✔DHCPv4:
▪ assigns IPv4 addresses and other network configuration information dynamically
▪ useful and timesaving tool for network administrators
▪ dynamically assigns, or leases, an IPv4 address from a pool of addresses
▪ A Cisco router can be configured to provide DHCPv4 services.
▪ Administrators configure DHCPv4 servers so that leases expire. Then the client must ask for another
address, although the client is typically reassigned the same address.
Configure a Basic DHCPv4 Server - correct answer ✔✔A Cisco router running the Cisco IOS software can
be configured to act as a DHCPv4 server. To set up DHCP:
1. 2. 3.
1 Exclude addresses from the pool.
2 Set up the DHCP pool name.
3 Define the range of addresses and subnet mask. Use the default-router command for the default
gateway. Optional parameters that can be included in the pool - dns server, domain-name.
To disable DHCP, use the no service dhcp command
Verifying DHCPv4 - correct answer ✔✔Commands to verify DHCP:
show running-config | section dhcp show ip dhcp binding
show ip dhcp server statistics
▪ On the PC, issue the ipconfig /all command.
DHCPv4 Relay - correct answer ✔✔▪ Using an IP helper address enables a router to forward DHCPv4
broadcasts to the DHCPv4 server. Acting as a relay.
Configure Cisco router as a DHCP client - correct answer ✔✔R1(config)#int Gi0/0
, R1(config-if)#ip address dhcp
A Cisco IOS device can be configured to act as: - correct answer ✔✔•a DHCP server - by providing IP
addresses when requested to do so
•a DHCP client - when it requests an IP address
•a DHCP relay agent - when it captures IP requests from clients, adds extra information to the request
for user identification purposes, and forwards the request to the DHCP server
Create a DHCP IP address pool for the IP addresses you want to use. - correct answer ✔✔1.Create a
DHCP IP address pool for the IP addresses you want to use.
Router(config)# ip dhcp pool mypool
2.Specify the network and subnet for the addresses you want to use from the pool.
Router(dhcp-config)# network 1.1.1.0 /8
3.Specify the DNS domain name for the clients.
Router(dhcp-config)#domain-name mydomain.com
4.Specify the primary and secondary DNS servers.
Router(dhcp-config)#dns-server 1.1.1.10 1.1.1.11
5.Specify the default router (i.e., default gateway).
Router(dhcp-config)#default-router 1.1.1.1
6.Specify the lease duration for the addresses you're using from the pool.
Router(dhcp-config)#lease 7
7.Exit Pool Configuration Mode.
Router(dhcp-config)#exit
Dynamic Host Configuration Protocol (DHCP) - correct answer ✔✔1.The client sends a DHCP Discover
message to locate a DHCP server - this is a broadcast message
2.The DHCP server responds with a DHCP Offer unicast message - this message includes the IP address
offered to the client, default gateway address and lease time for the IP address offered; it may also
include DNS servers, TFTP server, and other information
3.The client responds with a DHCP Request message which is a formal request for the IP address offered
by the server - this is again a broadcast message
Introducing DHCPv4 - correct answer ✔✔DHCPv4:
▪ assigns IPv4 addresses and other network configuration information dynamically
▪ useful and timesaving tool for network administrators
▪ dynamically assigns, or leases, an IPv4 address from a pool of addresses
▪ A Cisco router can be configured to provide DHCPv4 services.
▪ Administrators configure DHCPv4 servers so that leases expire. Then the client must ask for another
address, although the client is typically reassigned the same address.
Configure a Basic DHCPv4 Server - correct answer ✔✔A Cisco router running the Cisco IOS software can
be configured to act as a DHCPv4 server. To set up DHCP:
1. 2. 3.
1 Exclude addresses from the pool.
2 Set up the DHCP pool name.
3 Define the range of addresses and subnet mask. Use the default-router command for the default
gateway. Optional parameters that can be included in the pool - dns server, domain-name.
To disable DHCP, use the no service dhcp command
Verifying DHCPv4 - correct answer ✔✔Commands to verify DHCP:
show running-config | section dhcp show ip dhcp binding
show ip dhcp server statistics
▪ On the PC, issue the ipconfig /all command.
DHCPv4 Relay - correct answer ✔✔▪ Using an IP helper address enables a router to forward DHCPv4
broadcasts to the DHCPv4 server. Acting as a relay.
Configure Cisco router as a DHCP client - correct answer ✔✔R1(config)#int Gi0/0
, R1(config-if)#ip address dhcp
A Cisco IOS device can be configured to act as: - correct answer ✔✔•a DHCP server - by providing IP
addresses when requested to do so
•a DHCP client - when it requests an IP address
•a DHCP relay agent - when it captures IP requests from clients, adds extra information to the request
for user identification purposes, and forwards the request to the DHCP server
Create a DHCP IP address pool for the IP addresses you want to use. - correct answer ✔✔1.Create a
DHCP IP address pool for the IP addresses you want to use.
Router(config)# ip dhcp pool mypool
2.Specify the network and subnet for the addresses you want to use from the pool.
Router(dhcp-config)# network 1.1.1.0 /8
3.Specify the DNS domain name for the clients.
Router(dhcp-config)#domain-name mydomain.com
4.Specify the primary and secondary DNS servers.
Router(dhcp-config)#dns-server 1.1.1.10 1.1.1.11
5.Specify the default router (i.e., default gateway).
Router(dhcp-config)#default-router 1.1.1.1
6.Specify the lease duration for the addresses you're using from the pool.
Router(dhcp-config)#lease 7
7.Exit Pool Configuration Mode.
Router(dhcp-config)#exit
Dynamic Host Configuration Protocol (DHCP) - correct answer ✔✔1.The client sends a DHCP Discover
message to locate a DHCP server - this is a broadcast message
2.The DHCP server responds with a DHCP Offer unicast message - this message includes the IP address
offered to the client, default gateway address and lease time for the IP address offered; it may also
include DNS servers, TFTP server, and other information
3.The client responds with a DHCP Request message which is a formal request for the IP address offered
by the server - this is again a broadcast message
