Which configuration command must be in effect to allow the use of 8 subnets if the Class C subnet mask is 255.255.255.224?
Options
A. Router(config)#ip classless
B. Router(config)#no ip classful
C. Router(config)#ip unnumbered
D. Router(config)#ip subnet-zero
Correct Answer
Router(config)#ip subnet-zero
Explanation
A Class C subnet mask of 255.255.255.224 is 3 bits on and 5 bits off (11100000) and provides 8 subnets, each with 30 hosts. However, if the command
ip subnet-zero is not used, then only 6 subnets would be available for use.
More questions
1. What does the command o/r 0x2142 provide?
Options
A. It is used to restart the router.
B. It is used to bypass the configuration in NVRAM.
Correct Answer: It is used to bypass the configuration in NVRAM.
Explanation:
The default configuration setting is
0x2102, which tells the router to load the IOS from flash and the configuration from NVRAM.
0x2142 tells the router to bypass the configuration in NVRAM so that you can perform password recovery.
2. The configuration register setting of 0x2102 provides what function to a router?
Options
A. Tells the router to boot into ROM monitor mode
B. Provides password recovery
C. Tells the router to look in NVRAM for the boot sequence
If you are on a 2950 switch, then the interface command is just
switchport mode trunk, since the 2950 can only run the IEEE 802.1Q version. However, a 3550 can run both ISL and 802.1Q, so you must use the encapsulation command. The argument to choose 802.1Q for a trunking protocol is
dot1q.
6. To test the IP stack on your local host, which IP address would you ping?
Loopback interfaces are created on a router, and the highest IP address on a loopback (logical) interface becomes the RID of the router but has nothing to do with areas and is optional, so (1) is wrong. The numbers you can create an area with are from 0 to 4,294,967,295 option (2) is wrong. The backbone area is called area 0, so option (3) is correct. All areas must connect to area 0, so option (5) is correct. If you have only one area, it must be called area 0. This leaves option (4), which must be correct; it doesn't make much sense, but it is the best answer.