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Subnetting and IPv4 Address Classes2005-10-20 (updated: 2009-11-09) by PhilipTags: subnet, IPv4, IP, IP Address, routable Subnetting Concept Subnetting an IP network allows for the flow of network traffic to be segregated based on a network configuration. It essentially organizes the hosts into logical groups, and provides for improving network security and performance. The most common reason for subnetting IP networks is to control network traffic. Traditionally, in an Ethernet network, it is very common for all nodes on a segment to see all the packets transmitted by all the other nodes on that segment, which introduces collisions, and the resulting retransmissions under heavy traffic loads. For additional information on subnetting, see RFC 1817, and RFC 1812.
IPv4 TCP/IP Subnet Table While subnetting might be easy enough to grasp as a concept, it can be a bit involved, and even mind-boggling in part due to the required manipulations of binary numbers. Many people understand the ideas behind subnetting, but find it hard to follow the actual steps required to subnet a network. The table bellow is intended as a quick reference and a fairly complete example of IPv4 subnetting.
* Usable Hosts - (2^N-2) method. ** Inverse mask is calculated by subtracting each subnet mask octet value from 255. The inverse mask is primarily used in Cisco access control lists (ACLs). The rationale behind an inverse mask is that logical ANDing an inverse mask and an IP address gives the host portion of the address, instead of the network / subner portion that a standard subnet mask would. This is of more interest to certain TCP/IP functions. Notes: Certain potions of the IPv4 address space are specifically allocated by RFCs for special uses, such as loopback (RFC 1643), private networks (RFC 1918), and zeroconf (RFC 3927) usage.
IPv4 Address Classes Class Address Ranges
Class A, Class B, and Class C are the three classes of addresses used on IP networks in common practice. Class D addresses are reserved for multicast. Class E addresses are simply reserved, meaning they should not be used on IP networks (used on a limited basis by some research organizations for experimental purposes).
Reserved Address Ranges Address ranges below are reserved by IANA for private intranets, and not routable to the Internet. For additional information, see RFC 1918.
Other reserved addresses:
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anonymous - 2007-05-02 07:46
Thanks, really nice explanation
What a good explanation.... Thanks a lot guys....
good reference for public..thanks,
Brief and concise
great explanation...thx a lot
Well,that explane alot :)
Class C - 192.0.0.0 to 223.255.255.255
My own correction :o)
Class C - 192.0.0.0 to 223.255.255.0
Thanks yaar, good one :)
Thank you so much,good material for beginner.
Hey, thanks for sharing a nice piece of information, but i have a query. My teacher told me that the valid network number in class B is from 128.1.0.0 till 191.254.0.0 and not 128.0.0.0 till 191.255.0.0. I am really confused why. Can any one please help me out?
it is realy good information to the classes of ipv4 addresses
This is the first time I'm commenting on an article because i found it immensely useful. You read this once and thats it, it just gets registered in your mind forever. Hats off to the author.
Great Reference
THANX well explained keep it up
GREAT SITE REALLY HELPFUL, I AM STUDYING FOR MY CCNA.
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