Planning and designing
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Questions derived from the 640-801 - Cisco Certified Network Associate (single-exam option) Cisco Self-Test Software Practice Test.
Objective: Planning and designing
SubObjective: Design an IP addressing scheme to meet design requirements
Item Number: 640-801.1.2.10
Single Answer, Multiple Choice
A service provider has been assigned the 192.168.0.0/16 address. Which of the following addresses is a valid host address for the CIDR block 192.168.8.0/21?
- 192.168.8.64/28
- 192.168.9.13/22
- 192.168.10.31/27
- 192.168.16.111/24
Answer:
B. 192.168.9.13/22
Tutorial:
The address 192.168.9.13 255.255.252.0 (or /22) is a valid address for the classless interdomain routing (CIDR) address 192.168.8.0/21.
CIDR enables a service provider to advertise a super-netted summary network address. If the service provider is assigned the 192.168.8.0 Class C address and the 255.255.252.0 network mask, they have more addresses available than if they were restricted to the 24-bit classful mask boundary. The service provider can then administer the new address space to its customers. The 192.168.9.13/22 address has the same first 21 bits the same as the 192.168.8.0/21 address.
The 192.168.8.64/28 address is an invalid host address. All host bits are off.
The 192.168.10.31/27 address is an invalid host address. All host bits are on.
The 192.168.16.111/24 address is a valid host address, but it does not reside in the 192.168.8.0/21 network.
For more information on the CIDR and VLSM, see: http://www.cisco.com/warp/public/701/3.html#vlsmexample
Reference:
INTRO Student Guide v1.0a - Volume 2 - IP Subnetting - Network Address Planning
