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Tuesday 7 February 2012

Summarization, Subnetting and Supernetting -difference


A subnet mask is used to identify which parts of the ip address are the network parts and which parts are the host parts. Here we are trying to find difference in terms  Summarization, Subnetting and Supernetting.

With only /24 networks in an enterprise, 10.1.0.0/16 may well be a summary.  10.0.0.0/8 is a summary address as well.  10.0.0.0/7  (including the 10.0.0.0/8 and 11.0.0.0/8 Class A's) is a supernet. It allows more host to be available for the network.

Let's take another example.. a class C mask of 255.255.255.0 and IP address 10.1.1.0 (10.1.1.1/24)-
If we borrow 2 network bits, the mask changes to 255.255.252.0(22) from 255.255.255.0(24), this is called supernetting. On the other hand we borrow two host bits, the mask changes to 255.255.255.192(26), this is called subnetting.

Here we can say 10.1.1.0/23 is supernet address of summary route 10.1.1.0/24  subnet address of 0.1.1.0/16
Similarly, 10.1.1.0/17 is subnet address of summary address 10.1.1.0/16 but it is supernet address of 10.1.1.0/24

So, in any case addresses with CIDR block  /8, /16, /24 can be termed as summary addresses but addresses with CIDR /7, /15, /17 are considered as subnetting/supernetting addresses bassed on borrowing of network/host bits.

Supernetting therefore allows you to have more hosts on one network, whereas subnetting allows you to have more inter networks but with less hosts.

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