255.255.255.248255.255.255.252Explain:If the same mask is to be used, then the network with the most hosts must beexamined for number of hosts. Because this is 10 hosts, 4 host bits are needed.The /28 or 255.255.255.240 subnet mask would be appropriate to use for thesenetworks.49. How many hosts are addressable on a network that has a mask of255.255.255.248?26*81416254Explain:The subnet mask of 255.255.255.248 is the same as /29. This means thenetwork portion of the address is 29 of the 32 bits in the address. Only 3 bitsremain for host bits. 2^3 = 8, but one of these addresses has to be used for thenetwork number and one address must be used as the broadcast address toreach all of the hosts on this network. That leaves only 6 usable IP addressesthat can be assigned to hosts in this network. Don’t forget that the defaultgateway must be one of these devices if this network is to communicate withother networks.50. Which subnet would include the address 192.168.1.96 as a usable hostaddress?192.168.1.64/26*192.168.1.32/27192.168.1.32/28192.168.1.64/29Explain:For the subnet of 192.168.1.64/26, there are 6 bits for host addresses, yielding64 possible addresses. However, the first and last subnets are the network andbroadcast addresses for this subnet. Therefore, the range of host addresses forthis subnet is 192.168.1.65 to 192.168.1.126. The other subnets do not containthe address 192.168.1.96 as a valid host address.51. What subnet mask is needed if an IPv4 network has 40 devices thatneed IP addresses and address space is not to be wasted?
Subnetting is the process of dividing one network into smaller networks. Collectively, the smaller networks are referred to as subnetworks [or subnets], and the singular subdivision is a subnetwork [more commonly referred to as a subnet]. Every single computer that is connected to a subnet shares an identical portion of the IP address. This shared information is known as a routing prefix, and in IPV4 [Internet Protocol Version 4], the routing prefix is called a subnet mask. The subnet mask is a "quad-dotted decimal representation".
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- Class address ranges:
- Reserved address ranges for private [non-routed] use:
- Other reserved addresses:
- Chart notes:
- How many valid node addresses are available in an IPv4 subnet 26 mask?
- How many valid host addresses are available on an IPv4 subnet that is configured with a slash 28 mask?
- Which subnet mask would be used if 5 host bits are available?
This IPv4 Subnet Chart can assist you in looking up how a network is broken up into subnets.
Class address ranges:
- Class A = 1.0.0.0 to 126.0.0.0
- Class B = 128.0.0.0 to 191.255.0.0
- Class C = 192.0.1.0 to 223.255.255.0
Reserved address ranges for private [non-routed] use:
- 10.0.0.0 -> 10.255.255.255
- 172.16.0.0 -> 172.31.255.255
- 192.168.0.0 -> 192.168.255.255
Other reserved addresses:
- 127.0.0.0 is reserved for loopback and IPC on the local host
- 224.0.0.0 -> 239.255.255.255 is reserved for multicast addresses
Chart notes:
- Number of Subnets - "[ ]" Refers to the number of effective subnets, since the use of subnet numbers of all 0s or all 1s is highly frowned upon and RFC non-compliant.
- Number of Hosts - Refers to the number of effective hosts, excluding the network and broadcast address.
Class A
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/8 | 255.0.0.0 | 0 | 16777214 |
/9 | 255.128.0.0 | 2 [0] | 8388606 |
/10 | 255.192.0.0 | 4 [2] | 4194302 |
/11 | 255.224.0.0 | 8 [6] | 2097150 |
/12 | 255.240.0.0 | 16 [14] | 1048574 |
/13 | 255.248.0.0 | 32 [30] | 524286 |
/14 | 255.252.0.0 | 64 [62] | 262142 |
/15 | 255.254.0.0 | 128 [126] | 131070 |
/16 | 255.255.0.0 | 256 [254] | 65534 |
/17 | 255.255.128.0 | 512 [510] | 32766 |
/18 | 255.255.192.0 | 1024 [1022] | 16382 |
/19 | 255.255.224.0 | 2048 [2046] | 8190 |
/20 | 255.255.240.0 | 4096 [4094] | 4094 |
/21 | 255.255.248.0 | 8192 [8190] | 2046 |
/22 | 255.255.252.0 | 16384 [16382] | 1022 |
/23 | 255.255.254.0 | 32768 [32766] | 510 |
/24 | 255.255.255.0 | 65536 [65534] | 254 |
/25 | 255.255.255.128 | 131072 [131070] | 126 |
/26 | 255.255.255.192 | 262144 [262142] | 62 |
/27 | 255.255.255.224 | 524288 [524286] | 30 |
/28 | 255.255.255.240 | 1048576 [1048574] | 14 |
/29 | 255.255.255.248 | 2097152 [2097150] | 6 |
/30 | 255.255.255.252 | 4194304 [4194302] | 2 |
Class B
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/16 | 255.255.0.0 | 0 | 65534 |
/17 | 255.255.128.0 | 2 [0] | 32766 |
/18 | 255.255.192.0 | 4 [2] | 16382 |
/19 | 255.255.224.0 | 8 [6] | 8190 |
/20 | 255.255.240.0 | 16 [14] | 4094 |
/21 | 255.255.248.0 | 32 [30] | 2046 |
/22 | 255.255.252.0 | 64 [62] | 1022 |
/23 | 255.255.254.0 | 128 [126] | 510 |
/24 | 255.255.255.0 | 256 [254] | 254 |
/25 | 255.255.255.128 | 512 [510] | 126 |
/26 | 255.255.255.192 | 1024 [1022] | 62 |
/27 | 255.255.255.224 | 2048 [2046] | 30 |
/28 | 255.255.255.240 | 4096 [4094] | 14 |
/29 | 255.255.255.248 | 8192 [8190] | 6 |
/30 | 255.255.255.252 | 16384 [16382] | 2 |
Class C
Network Bits | Subnet Mask | Number of Subnets | Number of Hosts |
/24 | 255.255.255.0 | 0 | 254 |
/25 | 255.255.255.128 | 2 [0] | 126 |
/26 | 255.255.255.192 | 4 [2] | 62 |
/27 | 255.255.255.224 | 8 [6] | 30 |
/28 | 255.255.255.240 | 16 [14] | 14 |
/29 | 255.255.255.248 | 32 [30] | 6 |
/30 | 255.255.255.252 | 64 [62] | 2 |
Class D
CIDR Block | Supernet Mask | Number of Class C Addresses | Number of Hosts |
/14 | 255.252.0.0 | 1024 | 262144 |
/15 | 255.254.0.0 | 512 | 131072 |
/16 | 255.255.0.0 | 256 | 65536 |
/17 | 255.255.128.0 | 128 | 32768 |
/18 | 255.255.192.0 | 64 | 16384 |
/19 | 255.255.224.0 | 32 | 8192 |
/20 | 255.255.240.0 | 16 | 4096 |
/21 | 255.255.248.0 | 8 | 2048 |
/22 | 255.255.252.0 | 4 | 1024 |
/23 | 255.255.254.0 | 2 | 512 |
How many valid node addresses are available in an IPv4 subnet 26 mask?
12. How many valid host addresses are available on an IPv4 subnet that is configured with a /26 mask? When a /26 mask is used, 6 bits are used as host bits. With 6 bits, 64 addresses are possible, but one address is for the subnet number and one address is for a broadcast.
How many valid host addresses are available on an IPv4 subnet that is configured with a slash 28 mask?
Explanation: A /28 mask is the same as 255.255. 255.240. This leaves 4 host bits. With 4 host bits, 16 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address.
Which subnet mask would be used if 5 host bits are available?
The mask of 255.255. 255.224 has 5 host bits.