Your network contains two DHCP servers. The DHCP servers are named DHCP1 and DHCP2. The
internal network contains 1,000 DHCP client computers that are located on a single subnet. A router
separates the internal network from the Internet. The router has a single IP address on the internal
interface. DHCP1 has the following scope information:
• Starting IP address: 172.16.0.1
• Ending IP address: 172.16.7.255
• Subnet mask: 255.255.240.0
You need to provide a fault tolerant DHCP infrastructure that supports the client computers on the
internal network. In the event that a DHCP server fails, all client computers must be able to obtain a
valid IP address.
How should you configure DHCP2?
A.
Create a scope for the subnet 172.16.0.0/20. Configure the scope to use a starting IP address of
172.16.8.1 and an ending IP address of 172.16.15.254.
B.
Create a scope for the subnet 172.16.0.0/21. Configure the scope to use a starting IP address of
172.16.0.1 and an ending IP address of 172.16.15.254.
C.
Create a scope for the subnet 172.16.8.0/21. Configure the scope to use a starting IP address of
172.16.8.1 and an ending IP address of 172.16.10.254.
D.
Create a scope for the subnet 172.17.0.0/16. Configure the scope to use a starting IP address of
172.17.0.1 and an ending IP address of 172.17.255.254.
Explanation:
Create a scope for the subnet 172.16.0.0/20.
Configure the scope to use a starting IP address of 172.16.8.1 and an ending IP address of
172.16.15.254.
Subnet 255.255.240.0 is a /20 subnet in CIDR notation, this allows for 4096 client IPs, ranging from
172.16.0.1 all the way to 172.16.15.254 as DHCP1 only used half of the available IPs then you should
configure DHCP2 to use the other half.
http ://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing as an aside you could consider the
80/20 design rule for balancing scope distribution of addresses where multiple DHCP servers are
deployed to service the same scope.
Using more than one DHCP server on the same subnet provides increased fault tolerance for
servicing DHCP clients located on it. With two DHCP servers, if one server is unavailable, the other
server can take its place and continue to lease new addresses or renew existing clients.
A common practice when balancing a single network and scope range of addresses between two
DHCP servers is to have 80 percent of the addresses distributed by one DHCP server and the
remaining 20 percent provided by a second.