Cisco CCNA mock exam questions sample test – Question 408

You have configured a router as shown in the following output:
Hosts on the LAN cannot receive an IP address. What is wrong?

A. The IP address on the serial interface is incorrect.
B. The default-router command in the DHCP pool is incorrect.
C. An IP address needs to be configured on the FastEthernet interface.
D. The NAT pool is not large enough.

Correct Answer: C

An IP address needs to be configured on the FastEthernet interface. Dynamic Host Control Protocol (DHCP) is used to dynamically provide IP network configurations to workstations as they are booted up. DHCP minimizes network administration overload, allowing devices to be added to the network with little or no manual configuration.
The router configuration in the scenario has created a DHCP address pool called POOLNAME. The network statement in the exhibit, network, identifies the range of IP addresses that the pool will provide to host systems ( /24). However, a DHCP pool can only provide IP addresses over a subnet to which it is directly connected.
Because neither of the interfaces in the exhibit has an IP address on the /24 subnet, the solution is to assign the FastEthernet0/0 interface the IP address specified in the default-router statement, /24.
The IP address on the serial interface has no impact on the DHCP pool.
The default-router statement is correctly providing the IP address that DHCP hosts will use as their default gateway. The problem is not with the default-router statement, but with the lack of a correct IP address assigned to the FastEthernet0/0 interface.
The NAT configuration in the exhibit has no impact on the DHCP pool. If the NAT pool were not large enough, the result would be that some of the hosts would be able to get to the Internet and others would not. For example, the output from the diagram shown below indicates that there are fourteen addresses in the pool ( to If the network contained 30 computers, only fourteen would be able to use the Internet at the same time because of the number of public addresses in the pool:
ip nat pool NATPOOL netmask
ip nat inside source list 1 pool NATPOOL

Infrastructure Services
Configure and verify DHCP on a router (excluding static reservations)
Cisco > Support > Cisco IOS Software > Configuring the Cisco IOS DHCP Server > Configuring DHCP Address Pools