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How to Use Wireshark to Capture, Filter and Inspect Packets. Wireshark, a network analysis tool formerly known as Ethereal, captures packets in real time and display them in human-readable format. Wireshark includes filters, color-coding and other features that let you dig deep into network traffic and inspect individual packets. This tutorial will get you up to speed with the basics of capturing packets, filtering them, and inspecting them. You can use Wireshark to inspect a suspicious program’s network traffic, analyze the traffic flow on your network, or troubleshoot network problems. Getting Wireshark You can download Wireshark for Windows or Mac OS X from its official website. Just a quick warning: Many organizations don’t allow Wireshark and similar tools on their networks. Capturing Packets After downloading and installing Wireshark, you can launch it and click the name of an interface under Interface List to start capturing packets on that interface.

Color Coding You’ll probably see packets highlighted in green, blue, and black. 5 Killer Tricks to Get the Most Out of Wireshark. Wireshark has quite a few tricks up its sleeve, from capturing remote traffic to creating firewall rules based on captured packets. Read on for some more advanced tips if you want to use Wireshark like a pro. We’ve already covered basic usage of Wireshark, so be sure to read our original article for an introduction to this powerful network analysis tool. Network Name Resolution While capturing packets, you might be annoyed that Wireshark only displays IP addresses. You can convert the IP addresses to domain names yourself, but that isn’t too convenient. Wireshark can automatically resolve these IP address to domain names, although this feature isn’t enabled by default.

You can enable this setting by opening the preferences window from Edit -> Preferences, clicking the Name Resolution panel and clicking the “Enable Network Name Resolution” check box. Start Capturing Automatically wireshark -i # -k For more command-line shortcuts, check out Wireshark’s manual page. tshark -i # -w filename. Packet Tracer. Cisco Packet Tracer is a powerful network simulation program that allows students to experiment with network behavior and ask “what if” questions. As an integral part of the Networking Academy comprehensive learning experience, Packet Tracer provides simulation, visualization, authoring, assessment, and collaboration capabilities and facilitates the teaching and learning of complex technology concepts. Packet Tracer supplements physical equipment in the classroom by allowing students to create a network with an almost unlimited number of devices, encouraging practice, discovery, and troubleshooting.

The simulation-based learning environment helps students develop 21st century skills such as decision making, creative and critical thinking, and problem solving. Packet Tracer complements the Networking Academy curricula, allowing instructors to easily teach and demonstrate complex technical concepts and networking systems design. Download Instructions Resources At-A-Glance (PDF) IP subnetting made easy. George Ou explains IP subnetting using his own graphical approach. It's a great primer for students and a nice refresher for others.

IP subnetting is a fundamental subject that's critical for any IP network engineer to understand, yet students have traditionally had a difficult time grasping it. Over the years, I've watched students needlessly struggle through school and in practice when dealing with subnetting because it was never explained to them in an easy-to-understand way. I've helped countless individuals learn what subnetting is all about using my own graphical approach and calculator shortcuts, and I've put all that experience into this article. IP addresses and subnets Although IP stands for Internet Protocol, it's a communications protocol used from the smallest private network to the massive global Internet. ...increment 252 hosts... ...increment 4+ billion hosts... The word subnet is short for sub network--a smaller network within a larger one. The graphical subnet ruler. VLAN. IT Certification and Training Blog.

NAT and PAT - What's the Difference? NAT and PAT - What's the Difference? Posted by Kelson Lawrence on Tue, Feb 08, 2011 @ 10:22 AM By Brian Scheibe Network Address Translation (NAT) and Port Address Translation (PAT) both map IP addresses on an internal network to IP addresses on an external network. Which method of address translation you use depends on the types of networks that you are translating and the number of available IP addresses that you have. If you are connecting a site in the 10.10.10.0 network to a site in the 10.10.20.0 network, you could use NAT to translate 10.10.10.0 IP addresses to available 10.10.20.0 IP addresses so that hosts on the 10.10.10.0 network can access data and use network resources on the 10.10.20.0 network.

PAT attempts to use the original source port number of the internal host to form a unique, registered IP address and port number combination. Interested in CCNA or CCNP certification? Nexus 5000 Series NX-OS Software Configuration Guide - Configuring VLANs [Cisco Nexus 5000 Series Switches] Configuring VLANs You can use virtual LANs (VLANs) to divide the network into separate logical areas. VLANs can also be considered as broadcast domains. Any switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and flooded only to end stations in that VLAN. Each VLAN is considered a logical network, and packets destined for stations that do not belong to the VLAN must be forwarded through a router. This chapter includes the following sections: Information About VLANs This section includes the following topics: Understanding VLANs Note VLAN Trunking Protocol (VTP) mode is OFF. A VLAN is a group of end stations in a switched network that is logically segmented by function, project team, or application, without regard to the physical locations of the users.

Any port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and flooded only to end stations in that VLAN. Figure 1-1 shows VLANs as logical networks. Configuring a VLAN. LAN Network Cable Media and Connectors | LAN Network Cable Media and Connectors. This article takes a look at the LAN network cable media that is typically installed in most environments and the different connectors that are often used.

Like this article? We recommend  When coming into the networking or Internet Technology (IT) field, it is often overwhelming, this is because there are so many different things that are expected to be known upfront. A common entry position is user support; this position requires that the individual have at least decent personal skills and at a minimum, a working knowledge of the systems the users utilize. These systems often include an operating system, a workstation, and a LAN connection to internal networking resources. Cable Media There are a number of different cabling types that a network engineer/administrator sees over the course of their career. Unshielded Twisted Pair (UTP) Table 1: UTP Cabling Categories Shielded Twisted Pair (STP) Multi-Mode Fiber (MMF) Single Mode Fiber (SMF) Connectors Registered Jack 45 (RJ45) Straight Tip (ST)

Cisco LAN Switching Fundamentals: Configuring Switches > An Ounce of Planning. This chapter covers the following topics: An ounce of planningConfiguration overviewInitial configurationConnecting the switchesConfiguring the access layerConfiguring SNMP Now that you have learned about the concepts behind Layer 2 and Layer 3 switching in some detail, you will focus on a start-to-finish configuration of a relatively simple campus switching design in this chapter.

Everyone has probably heard the old joke "ready, fire, aim. " Unfortunately, this phrase can sometimes describe the implementation of some networks given what appears to be a lack of basic planning prior to configuration. The daily operation of a switched environment can be greatly simplified and future problems avoided by applying a few best practices and a little bit of planning. Management Interfaces Out-of-band management is achieved initially through the serial console port on the Supervisor module. Sc0 and VLAN 1 All switchports must be members of a VLAN, and, by default, it is VLAN 1. Routing 101: The Basics  [Networking Fundamentals] In a small business LAN, the primary networking devices are network interface cards (NICs), that connect PC's and servers to the LAN, and Hubs and/or switches that interconnect the various LAN devices and create the Ethernet backbone. These devices operate at Layer 2 (the data link layer) of the OSI reference model.

For the LAN users to connect to the Internet or to a remote branch office a device called a router must be used. A router passes data between multiple networks. It works at the OSI Network Layer (Layer3), which means that it must be able to understand the data packets so that it can route them to their destination. They are essentially computers optimized for handling packets that have to be transferred between separate networks. Routers attempt to send packets from their source to their destination in the fastest way possible which is not always the absolute shortest path. Routing between a LAN and WAN is like a postal system or a courier network. How does a router do this? The Undersea Cables that Connect the World. What you see above is a submarine communications cable. With a diameter of 69 millimeter (2.7 inches), it carries 99% of all international traffic (i.e., internet, telephony and private data) and connects every continent on Earth with the exception of Antarctica.

These amazing fibre optic cables traverse oceans and span hundreds of thousands of kilometers. Below you will find pictures, descriptions and links to much more informative resources about this incredible network of cables that connect our planet. Map of the Worldwide Undersea Submarine Cable Network This is a map of all undersea cables around the world. It is a screen capture from an interactive website that let’s you zoom, pan and locate every known submarine cable in the world. This is the CS Cable Innovator, it is specifically designed for laying fiber optic cable and is the largest of its kind in the world [source]. Originally, submarine cables were simple point-to-point connections. 1. Submarine Cable Map 2014. Comprehensive Guide to Configuring and Troubleshooting Frame Relay. Introduction Frame Relay is an industry-standard, switched data link layer protocol that handles multiple virtual circuits using High-Level Data Link Control (HDLC) encapsulation between connected devices.

In many cases, Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement. The following figure illustrates a Frame Relay frame (ANSI T1.618). Note in the above figure, Q.922 addresses, as presently defined, are two octets and contain a 10-bit data-link connection identifier (DLCI). The "flag" fields delimit the beginning and end of the frame. The 10-bit DLCI value is the heart of the Frame Relay header. Before You Begin Conventions Refer to Cisco Technical Tips Conventions for more information on document conventions. Prerequisites For more information and definitions for the terms used in this document, please refer to the Frame Relay Glossary.

Components Used This document is not restricted to specific software and hardware versions. Spicey Aton. Troubleshooting PPP (CHAP or PAP) Authentication. Introduction Point-to-Point Protocol (PPP) authentication issues are one of the most common causes for dialup link failures. This document provides some troubleshooting procedures for PPP authentication issues. Prerequisites Enable debug ppp negotiation and debug ppp authentication. Terminology Local machine (or local router) - This is the system on which the debugging session is currently being run. Note: The terms local machine and peer do not imply a client-server relationship. Requirements Cisco recommends that you have knowledge of this topic: You must be able to read and understand the debug ppp negotiation output. Components Used This document is not restricted to specific software and hardware versions.

Conventions Refer to Cisco Technical Tips Conventions for more information on document conventions. Troubleshooting Flowchart This document includes some flowcharts to assist in troubleshooting. Is the Router Performing CHAP or PAP Authentication? Look for CHAP in the AUTHENTICATING phase: Subnetting made easy subnet 101 Only 16 minutes to become Subnet Guru! Configuring IP Access Lists. Introduction This document describes how IP access control lists (ACLs) can filter network traffic. It also contains brief descriptions of the IP ACL types, feature availability, and an example of use in a network. Access the Software Advisor (registered customers only) tool in order to determine the support of some of the more advanced Cisco IOS® IP ACL features. contains assigned numbers of well-known ports.

RFC 1918 contains address allocation for private Internets, IP addresses which should not normally be seen on the Internet. Note: ACLs might also be used for purposes other than to filter IP traffic, for example, defining traffic to Network Address Translate (NAT) or encrypt, or filtering non-IP protocols such as AppleTalk or IPX. Prerequisites Requirements There are no specific prerequisites for this document. Components Used This document discusses various types of ACLs. The information in this document was created from the devices in a specific lab environment. Conventions ACL Concepts. Home - Networking Academy.