The IPV4 addressing scheme was established long before the creation of what we know as the Internet. It's a bit of a schema that has 32 address a finite number of IP addresses for a little less than 4.3 billion. We have reached a point where the pool of available addresses is almost exhausted.
IPv6 is 128 bit addressing scheme that will ensure a significant increase as the Internet continues to grow, but is still a large part of the play is IPv4. First solution to IPv4 a lot less complicated than the IPv6 and IPv4 addresses now we use more effectively thanks to variable-length subnet mask (VLSM) to help reduce the number of unusable addresses, widely disseminated with the old-fashioned subnets, is widely used in the 1990s.
VLSM allows you to use more than one subnet mask in the network. In doing so, he takes the wasted addresses on a subnet and puts them into smaller subnets, so that they can be used. A common scenario would see large subnets used for hosts on a local area network (LAN) and a number of small subnets used for wide area network (WAN) links that joins LANs.
Here is an example of the subnet in the subnet:
Subnet 1:
192.168.1.0/27 (reserved for the network)
192.168.1.1/27 192.168.1.30/27 (range)
192.168.1.31/27 (used for broadcasting)
# 2:
192.168.1.32/27 (reserved for the network)
192.168.1.33/27 192.168.1.62/27 (range)
192.168.1.63/27 (reserved for broadcast)
# 3:
192.168.1.64/27 (Subnetted at 8 smaller subnet)
Small subnet 1:
192.168.1.64/30 (reserved for the network)
192.168.1.65/30 192.168.1.66/30 (range)
192.168.1.67/30 (used for broadcasting)
# 2:
192.168.1.68/30 (reserved for the network)
192.168.1.69/30 192.168.1.70/30 (range)
192.168.1.71/30 (reserved for broadcast)
# 3:
192.168.1.72/30 (reserved for the network)
192.168.1.73/30 192.168.1.74/30 (range)
192.168.1.75/30 (used for broadcasting)
# 4:
192.168.1.76/30 (reserved for the network)
192.168.1.77/30 192.168.1.78/30 (range)
192.168.1.79/30 (reserved for broadcast)
# 5:
192.168.1.80/30 (reserved for the network)
192.168.1.81/30 192.168.1.82/30 (range)
192.168.1.83/30 (used for broadcasting)
# 6:
192.168.1.84/30 (reserved for the network)
192.168.1.85/30 192.168.1.86/30 (range)
192.168.1.87/30 (reserved for broadcast)
# 7:
192.168.1.88/30 (reserved for the network)
192.168.1.89/30 192.168.1.90/30 (range)
192.168.1.91/30 (used for broadcasting)
# 8:
192.168.1.92/30 (reserved for the network)
192.168.1.93/30 192.168.1.94/30 (range)
192.168.1.95/30 (reserved for broadcast)
Subnet 4:
192.168.1.96/27 (reserved for the network)
192.168.1.97/27 192.168.1.126/27 (range)
192.168.1.127/27 (used for broadcasting)
# 5:
192.168.1.128/27 (reserved for the network)
192.168.1.129/27 192.168.1.158/27 (range)
192.168.1.159/27 (reserved for broadcast)
# 6:
192.168.1.160/27 (reserved for the network)
192.168.1.161/27 192.168.1.190/27 (range)
192.168.1.191/27 (used for broadcasting)
# 7:
192.168.1.192/27 (reserved for the network)
192.168.1.193/27 192.168.1.222/27 (range)
192.168.1.223/27 (reserved for broadcast)
# 8:
192.168.1.224/27 (reserved for the network)
192.168.1.225/27 192.168.1.254/27 (range)
192.168.1.255/27 (used for broadcasting)
How do we find all subnets with the exception of subnet 3 are 30 use IP addresses; Subnet 3 consists of 8 smaller subnets, each of which contains 2 use IP addresses, which is the perfect number for WAN links.
You may be wondering what is with the/27 and/30 suffixes? Where is the subnet mask? /27 and/30 is just another way of expressing a subnet mask by using VLSM suffixes. Here's how it works:
11111111.11111111.11111111.11111111
00000000.00000000.00000000.00000000
There are 32 bits in the subnet mask with the 4 octets, containing 8 bits.
Here is a table showing the decimal value of each bit in the octet:
128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
We can tell from this table as a reference:
1-th bit of the octet is 128
2nd bit in the octet is 64
3-th bit of the octet is 32
4-th bit of the octet is 16
5-th bit of the octet is 8
6-th bit of the octet is 4
7-th bit of the octet is 2
8-th bit of the octet is 1
The following subnet mask: 192.168.1.0/27 looks like binary 11111111.11111111.11111111.11100000
We can see that 3 bits were used to create large 8 subnets and the remaining 5 bits are used in such a way that each subnet can have 30 use host addresses. In the example above, the subnet 3 was divided into 8 small subnet which use/30 suffix and each contains 4 addresses (2 used addresses plus network address and broadcast address), which is the perfect number for WAN links.
The following subnet mask: 192.168.1.64/30 looks like in a binary 11111111.11111111.11111111.11111100
Note that the 6 bits were used for the subnet, which creates 64 subnets, but we use only 8 of them, because more subnet (subnet 3) can only contain 32 addresses. The remaining 2 bits are used for the host address, which gives 2 use small subnet.
The addressing scheme that is used in this article will allow you to create a number of medium-sized subnets and many small subnets; This is ideal for business with many different offices across multiple sites. It is safe, but more to the point, it's much less wasteful way to create subnets, than just using a subnet mask of the traditional.
My name is Jason Woodruff, and I work for global resources LTD. Miragetek I am working in the it industry, here's a link to our site:
http://www.miragetekshop.co.uk/
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