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 faulttolerant 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.