VLSM CIDR SUPERNET Difference

What is the difference between VLSM and CIDR and Supernetting?

• VLSM stands for Variable Length Subnet Mask
• CIDR stands for Classless Interdomain Routing.
• VLSM is for efficient use of ip addresses by avoiding wasteful allotment .Whereas CIDR is for reducing the number of entries in routing table by grouping related entries and making a supernet.

 

How IP addresses were wasted before invention of VLSM?

• Before implementation of VLSM, people were using Class A,B,C type of addressing. If a company wants just 20 addresses, the company was allotted with a class-C address which consists of 256 addresses.
• If a company wants 500 ip addresses, it will be allotted with a class-B address which is 256x256= 65,536 ip addresses.

In case of vlsm, if i asked 20 ip addresses, how many ip addresses will be allotted?

• The nearest power of 2, which means 2 power 5=32. Hence 32 ip addresses will be allotted to the company.

What is supernet?

• Supernetting is nothing but cidr. It is mainly used in routing table to reduce the number of routing table entries by grouping the related entries. In otherwords, a number of related subnets are grouped togther and formed a bigger subnet called as supernet.
• supernettting is aggregation of ip network addresses for the purpose of routing or advertising.

 

Mar 23,2009