168 lines
7.8 KiB
TeX
168 lines
7.8 KiB
TeX
%! TeX program = lualatex
|
|
\documentclass[a4paper]{article}
|
|
|
|
% packages
|
|
\usepackage{microtype} % Slightly tweak font spacing for aesthetics
|
|
\usepackage[english]{babel} % Language hyphenation and typographical rules
|
|
\usepackage[final, colorlinks = false, urlcolor = cyan]{hyperref}
|
|
\usepackage{changepage} % adjust margins on the fly
|
|
|
|
\usepackage{fontspec}
|
|
\setmainfont{EB Garamond}
|
|
\setmonofont[Scale=MatchLowercase]{Deja Vu Sans Mono}
|
|
|
|
\usepackage{minted}
|
|
\usepackage{xcolor}
|
|
|
|
\usepackage{pgfplots}
|
|
\pgfplotsset{width=\textwidth,compat=1.9}
|
|
|
|
\usepackage{caption}
|
|
\newenvironment{code}{\captionsetup{type=listing}}{}
|
|
% \captionsetup[listing]{font=small, skip=0pt}
|
|
% \setlength{\abovecaptionskip}{0pt}
|
|
% \setlength{\belowcaptionskip}{5pt}
|
|
|
|
\usepackage[yyyymmdd]{datetime}
|
|
\renewcommand{\dateseparator}{--}
|
|
|
|
\usepackage{titlesec}
|
|
% \titleformat{\section}{\LARGE\bfseries}{}{}{}[\titlerule]
|
|
% \titleformat{\subsection}{\Large\bfseries}{}{0em}{}
|
|
% \titlespacing{\subsection}{0em}{-0.7em}{0em}
|
|
%
|
|
% \titleformat{\subsubsection}{\large\bfseries}{}{0em}{$\bullet$ }
|
|
% \titlespacing{\subsubsection}{1em}{-0.7em}{0em}
|
|
|
|
% margins
|
|
\addtolength{\hoffset}{-2.25cm}
|
|
\addtolength{\textwidth}{4.5cm}
|
|
\addtolength{\voffset}{-3.25cm}
|
|
\addtolength{\textheight}{5cm}
|
|
\setlength{\parskip}{0pt}
|
|
\setlength{\parindent}{0in}
|
|
% \setcounter{secnumdepth}{0}
|
|
|
|
\begin{document}
|
|
\hrule \medskip
|
|
\begin{minipage}{0.295\textwidth}
|
|
\raggedright
|
|
\footnotesize
|
|
Name: Andrew Hayes \\
|
|
E-mail: \href{mailto://a.hayes18@universityofgalway.ie}{\texttt{a.hayes18@universityofgalway.ie}} \hfill\\
|
|
ID: 21321503 \hfill
|
|
\end{minipage}
|
|
\begin{minipage}{0.4\textwidth}
|
|
\centering
|
|
\vspace{0.4em}
|
|
\Large
|
|
\textbf{CT3531} \\
|
|
\end{minipage}
|
|
\begin{minipage}{0.295\textwidth}
|
|
\raggedleft
|
|
\today
|
|
\end{minipage}
|
|
\medskip\hrule
|
|
\begin{center}
|
|
\normalsize
|
|
Assignment 01: Expand the VLAN-Based Network
|
|
\end{center}
|
|
\hrule
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.8\textwidth]{./images/one.png}
|
|
\caption{Network Topology}
|
|
\end{figure}
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.635\textwidth]{./images/router_conf.png}
|
|
\caption{Router Configuration}
|
|
\end{figure}
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.6\textwidth]{./images/switch_conf.png}
|
|
\caption{Configuration of the New IT101 Switch}
|
|
\end{figure}
|
|
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.45\textwidth]{./images/five.png}
|
|
\caption{Verifying that The New VPC Devices in the Accounts VLAN Can Ping Each Other}
|
|
\end{figure}
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.5\textwidth]{./images/six.png}
|
|
\caption{Running a Trace from a VPC to Another VPC in the Same VLAN (Same VPCs as in Above Figure)}
|
|
\end{figure}
|
|
|
|
When we run a trace from Accounts-PC1 to Accounts-PC2 (which are both on VLAN150), we can see that it only takes one hop to get from Accounts-PC1 to Accounts-PC2.
|
|
Because these devices are in the same VLAN, they do not need to go through the router to address each other, and can reach other directly.
|
|
When devices share a VLAN, they can communicate directly at the Data Link Layer.
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.9\textwidth]{./images/seven.png}
|
|
\caption{Running a Trace from a VPC to Another VPC in Different VLANs}
|
|
\end{figure}
|
|
|
|
When we run a trace from Accounts-PC1 to Support-PC1 (which are on different VLANs), we can see that it takes two hops to get from Accounts-PC1 to Support-PC1.
|
|
Communication between separate VLANs requires routing, and therefore communicating between two devices on two different VLANs requires that the packets go through a
|
|
router.
|
|
The first IP in the trace is that of the router: \verb|192.168.150.1| (or rather the IP of the gateway of VLAN150 on the router).
|
|
The second IP in the trace is that of Support-PC1: \verb|192.168.200.254|.
|
|
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=\textwidth]{./images/eight.png}
|
|
\caption{Packet Capture on the Link Connecting the Switch \& the Router During a Ping between VPCs on Different VLANs}
|
|
\end{figure}
|
|
|
|
The general outline of what happened in this packet capture is as follows:
|
|
\begin{enumerate}
|
|
\item An ICMP ping is sent from Accounts-PC1 (which is on VLAN150) to Support-PC1 (which is on VLAN200).
|
|
Ethernet frames that travel between VLANs need a tag that identifies the VLAN as per the 802.1Q protocol.
|
|
However, the 802.1Q is not added by the VPC sending the ping; instead, the tag is added by the first switch that the frame passes through, in this case
|
|
the IT101 switch.
|
|
The IT101 switch will have encapsulated the packet with an 802.1Q header and added the VLAN information, including the priority bits, the VLAN ID of the
|
|
VLAN to which the packet belongs, \& the Canonical Format Indicator which indicates the canonical format of the MAC address.
|
|
Therefore, by the time the packet reaches the Switch1-Floor2 switch, the VLAN tag has already been added to the frame.
|
|
|
|
\item The Switch1-Floor2 switch then forwards the encapsulated packet which now contains the 802.1Q header to the Office-Router router.
|
|
This can be seen in the first ICMP packet that we captured going from \verb|192.168.150.254| (Accounts-PC1) to \verb|192.168.200.254| (Support-PC1):
|
|
\begin{figure}[H]
|
|
\centering
|
|
\includegraphics[width=0.9\textwidth]{./images/dot1q_tag.png}
|
|
\caption{ICMP Packet Containing the 802.1Q Tag}
|
|
\end{figure}
|
|
|
|
\item We can tell what links require an 802.1Q header by checking whether they are trunks or access links: trunks expect packets to have an 802.1Q header so
|
|
that the switches or routers that they are linking can know which VLAN they belong to.
|
|
Access links do not expect an 802.1Q header, as the ports which access links join are specified to belong to a certain VLAN when the switch is configured.
|
|
Therefore every packet traversing one of the trunk links, i.e. IT101 {\leftrightarrow} Switch1-Floor2, Switch1-Floor2 {\leftrightarrow} Office-Router,
|
|
\& Switch1-Floor2 {\leftrightarrow} Switch2-Floor2, requires a 802.1Q header.
|
|
The last switch (Switch2-Floor2) before the destination VPC (Support-PC1) will remove the 802.1Q header, extracting the original ICMP echo request packet, and send it
|
|
down the access link to Support-PC1.
|
|
|
|
\item The router is needed to facilitate the inter-VLAN communication;
|
|
although, in purely physical terms, data could be transferred via the switches from Accounts-PC1 to Support-PC1 without having to go to the router, the
|
|
router is needed to facilitate inter-VLAN communication over IP, as the VLANs have separate broadcast domains and the individual VPCs do not know which
|
|
VLAN they belong to, if any.
|
|
The router forwards the packets to the switch Switch1-Floor2, which passes them to Switch2-Floor2.
|
|
|
|
\item When the ICMP packets reach Switch2-Floor2, the 802.1Q header is stripped from them, as they have now traversed the last trunk link that they need to
|
|
and are now going to pass over an access port to Support-PC1.
|
|
Since we are capturing the packets over the trunk link between a Switch1-Floor2 \& Office-Router, we will never see a packet without an 802.1Q header,
|
|
although they are in use for this ping.
|
|
|
|
\item When the echo request reaches Support-PC1, it send back an echo reply via Switch2-Floor2.
|
|
The 802.1Q header will be added at Switch2-Floor2, and the process will repeat to route the packet across the trunks to the router, and then to the
|
|
IT101 switch, where the 802.1Q header will be stripped and the packet forwarded back to Accounts-PC1, completing the ping.
|
|
\end{enumerate}
|
|
|
|
\end{document}
|