Maximum Number of Usable IP Addresses for Each LAN | Cisco Certified Network Associate Exam

# Max Usable IP Addresses for Each LAN

### Question

The network administrator needs to address seven LANs. RIP version 1 is the only routing protocol in use on the network and subnet 0 is not being used. What is the maximum number of usable IP addresses that can be supported on each LAN if the organization is using one class C address block?

### Explanations

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A. B. C. D. E. F.

C

The organization is using one Class C address block, which means that the network administrator has been allocated a block of IP addresses in the range of 192.0.0.0 to 223.255.255.255.

Since RIP version 1 is the only routing protocol in use, we can assume that the network administrator has chosen to use a subnet mask of 255.255.255.0 (/24) on each LAN.

Subnet 0 is not being used, which means that the first subnet available is subnet 1.

To calculate the maximum number of usable IP addresses on each LAN, we need to subtract two addresses from the total number of addresses in the subnet. The two addresses that need to be subtracted are the network address and the broadcast address.

For example, if the first LAN is assigned the subnet 192.168.1.0/24, the network address is 192.168.1.0 and the broadcast address is 192.168.1.255. Therefore, the maximum number of usable IP addresses on this LAN is:

2^8 - 2 = 256 - 2 = 254

So, the answer to the question is:

The maximum number of usable IP addresses that can be supported on each LAN if the organization is using one Class C address block with a subnet mask of 255.255.255.0 and RIP version 1 is the only routing protocol in use is 254.