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% Most of the following are not required for the majority
% of cheat sheets but are needed for some symbol support.
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% Document Info
\author{bytebar}
\pdfinfo{
  /Title (subnetting-cheat-sheet.pdf)
  /Creator (Cheatography)
  /Author (bytebar)
  /Subject (Subnetting Cheat Sheet)
}

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\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Subnetting Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{bytebar} via \textcolor{DarkBackground}{\uline{cheatography.com/218949/cs/48434/}}}
\end{tabulary}
\end{multicols}}

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\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}bytebar \\
  \uline{cheatography.com/bytebar} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Published 14th September, 2026.\\
   Updated 14th September, 2026.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
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  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
\raggedright
\raggedcolumns

% Set font size to small. Switch to any value
% from this page to resize cheat sheet text:
% www.emerson.emory.edu/services/latex/latex_169.html
\footnotesize % Small font.

\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Intro}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{The 30-second subnetting trick, CIDR tables, and everything CompTIA and Cisco expect you to know cold.% Row Count 3 (+ 3)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Intro text}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{The Subnetting Trick (do this on every question)}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Given an IP and CIDR (e.g. 192.168.1.77/26): \newline % Row Count 1 (+ 1)
1. Block size = 256 − interesting octet value → 256 − 192 = 64 \newline % Row Count 3 (+ 2)
2. Subnets fall on multiples of the block size → 0, 64, 128, 192 \newline % Row Count 5 (+ 2)
3. 77 falls between 64 and 128 → subnet is 192.168.1.64 \newline % Row Count 7 (+ 2)
4. Range: 192.168.1.64 – 192.168.1.127 · Broadcast: .127 · Usable: .65 – .126% Row Count 9 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Subnetting trick steps}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.66832 cm} x{1.21133 cm} x{1.00248 cm} x{1.29487 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{5.377cm}}{\bf\textcolor{white}{CIDR Quick Table}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{CIDR}} & {\bf{Subnet Mask}} & {\bf{Wildcard}} & {\bf{Usable Hosts}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
/24 & \seqsplit{255.255.255.0} & \seqsplit{0.0.0.255} & 254 \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
/25 & \seqsplit{255.255.255.128} & \seqsplit{0.0.0.127} & 126 \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
/26 & \seqsplit{255.255.255.192} & 0.0.0.63 & 62 \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
/27 & \seqsplit{255.255.255.224} & 0.0.0.31 & 30 \tn 
% Row Count 10 (+ 2)
% Row 5
\SetRowColor{white}
/28 & \seqsplit{255.255.255.240} & 0.0.0.15 & 14 \tn 
% Row Count 12 (+ 2)
% Row 6
\SetRowColor{LightBackground}
/29 & \seqsplit{255.255.255.248} & 0.0.0.7 & 6 \tn 
% Row Count 14 (+ 2)
% Row 7
\SetRowColor{white}
/30 & \seqsplit{255.255.255.252} & 0.0.0.3 & 2 \tn 
% Row Count 16 (+ 2)
% Row 8
\SetRowColor{LightBackground}
/23 & \seqsplit{255.255.254.0} & \seqsplit{0.0.1.255} & 510 \tn 
% Row Count 18 (+ 2)
% Row 9
\SetRowColor{white}
/22 & \seqsplit{255.255.252.0} & \seqsplit{0.0.3.255} & 1,022 \tn 
% Row Count 20 (+ 2)
% Row 10
\SetRowColor{LightBackground}
/21 & \seqsplit{255.255.248.0} & \seqsplit{0.0.7.255} & 2,046 \tn 
% Row Count 22 (+ 2)
% Row 11
\SetRowColor{white}
/16 & \seqsplit{255.255.0.0} & \seqsplit{0.0.255.255} & 65,534 \tn 
% Row Count 24 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{5.377cm}}{Formula: usable hosts = 2\textasciicircum{}(host bits) − 2 (subtract network + broadcast)}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.62655 cm} x{2.13027 cm} p{0.54301 cm} x{0.87717 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{5.377cm}}{\bf\textcolor{white}{Private IP Ranges (RFC 1918)}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Class}} & {\bf{Range}} & {\bf{CIDR}} & {\bf{Addresses}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
A & 10.0.0.0 – 10.255.255.255 & /8 & 16,777,216 \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
B & 172.16.0.0 – 172.31.255.255 & /12 & 1,048,576 \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
C & 192.168.0.0 – 192.168.255.255 & /16 & 65,536 \tn 
% Row Count 8 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{5.377cm}}{Also know: 127.0.0.0/8 = loopback · 169.254.0.0/16 = APIPA (link-local, DHCP failed)}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.05271 cm} x{1.73926 cm} x{1.78503 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Classful Boundaries}}  \tn
% Row 0
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{\bf{Class}} & {\bf{First Octet}} & {\bf{Default Mask}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
A & 1 – 126 & /8 \tn 
% Row Count 3 (+ 1)
% Row 2
\SetRowColor{LightBackground}
B & 128 – 191 & /16 \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
C & 192 – 223 & /24 \tn 
% Row Count 5 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{(127 is reserved — loopback, not Class A usable.)}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.4931 cm} x{3.4839 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Special-Purpose Addresses}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Address}} & {\bf{Meaning}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
0.0.0.0/0 & Default route — "everything" \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\seqsplit{255.255.255.255} & Limited broadcast — "everyone here" \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
Network address & First address in subnet (not assignable) \tn 
% Row Count 7 (+ 2)
% Row 4
\SetRowColor{LightBackground}
Broadcast address & Last address in subnet (not assignable) \tn 
% Row Count 9 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Special addresses to know}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{More from ByteBar}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Full subnetting walkthroughs + practice questions at bytebarhq.com — by ByteBar.% Row Count 2 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Footer}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}