Variable Length Subnet Table For IPv4 (RFC1878)
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
T. Pummill: AUTHOR [+1]
This memo clarifies issues surrounding subnetting IP networks by providing a standard subnet table. This table includes subnetting for Class A, B, and C networks, as well as Network IDs, host ranges and IP broadcast addresses with emphasis on Class C subnets.
Network Working Group T. Pummill
Request for Comments: 1878 Alantec
Obsoletes: 1860 B. Manning
Category: Informational ISI
Variable Length Subnet Table For IPv4
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
This memo clarifies issues surrounding subnetting IP networks by
providing a standard subnet table. This table includes subnetting
for Class A, B, and C networks, as well as Network IDs, host ranges
and IP broadcast addresses with emphasis on Class C subnets.
This memo is intended as an informational companion to Subneting RFC
 and the Hosts Requirements RFC .
The growth of networking since the time of STD 5, RFC 950 and STD 3,
RFC 1123 has resulted in larger and more complex network subnetting.
The previously mentioned RFCs comprise the available guidelines for
creating subnetted networks, however they have occassionaly been
misinterpreted leading to confusion regarding proper subnetting.
This document itemizes the potential values for IPv4 subnets.
Additional information is provided for Hex and Decmial values,
classfull equivalants, and number of addresses available within the
The following table lists the variable length subnets from 1 to 32,
the CIDR  representation form (/xx) and the Decmial equivalents.
(M = Million, K=Thousand, A,B,C= traditional class values)
Mask value: # of
Hex CIDR Decimal addresses Classfull
80.00.00.00 /1 184.108.40.206 2048 M 128 A
C0.00.00.00 /2 192.0.0.0 1024 M 64 A
E0.00.00.00 /3 220.127.116.11 512 M 32 A
F0.00.00.00 /4 240.0.0.0 256 M 16 A
F8.00.00.00 /5 248.0.0.0 128 M 8 A
FC.00.00.00 /6 252.0.0.0 64 M 4 A
FE.00.00.00 /7 254.0.0.0 32 M 2 A
FF.00.00.00 /8 255.0.0.0 16 M 1 A
FF.80.00.00 /9 255.128.0.0 8 M 128 B
FF.C0.00.00 /10 255.192.0.0 4 M 64 B
FF.E0.00.00 /11 255.224.0.0 2 M 32 B
FF.F0.00.00 /12 255.240.0.0 1024 K 16 B
FF.F8.00.00 /13 255.248.0.0 512 K ...