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5.3 Given a scenario, use the appropriate network software tools and commands

Last edited 1062 days ago by Makiel [Muh-Keel].

Software Tools

Knowledge of how to use these tools allows you to locate, troubleshoot, and resolve any networking issues you may come across.

Wi-Fi analyzers

Can look into the air and gather valuable information such as signal levers, noise readings, SSIDs, and interference to resolve most Wi-Fi related issues. You can see the Wi-Fi coverage in an area and use that information for optimal access-point placement to get complete coverage and avoid dead spots

Protocol Analyzers

Also called sniffers, used to capture packets in their raw format as they cross the network. Protocol analyzers can be used to determine the type of traffic that you have in your network, and depending on the product and the bells and whistles contained, you may also be able to sort the results based on port numbers, protocols, and so on. Another use of a sniffer is to examine the traffic that should be occurring on the network when something is not working to aid in troubleshooting.

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Bandwidth Testers

These devices, typically software based, work much like a protocol analyzer in that they measure the traffic seen on the network and can also classify the types of traffic that are eating up your bandwidth.

Compare the baseline data throughput measurements to the Bandwidth Tester Network throughput measurements to determine whether or not data rates are within normal range.

How do you know what is abnormal when you don't know what normal is?

IPerf is an open-source software tool that measures network throughput and is very handy for testing and creating baselines of your network. The software runs as a server on one end and a client on the other.

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Port Scanner

A software tool designed to search a network for hosts with open ports. Those of us administering our networks use port scanners to ensure their security, but bad guys use them to find a network's vulnerabilities and compromise them.

To port scan means to scan for TCP and UDP open ports on a single target host to and use its services for good reasons or bad. Use Port scan to find open ports and actively secure them.

It's a really good idea to turn off any unused services on your servers and routers and to run only the minimum services required on every host machine in your network.

NetFlow analyzers

Collects information on each unique traffic flow into and out of a network device interfaces. NetFlow allows for the viewing and analysis of application-level traffic across an interface. NetFlow collects source and destination addresses, application information, and quality of service (QoS) data and is very helpful in troubleshooting causes of networking problems.

NetFlow analyzes the data and creates reports, charts, graphs, and sometimes analytics on the received information.

TFTP (Trivial File Transfer Protocol)

Used to transfer networking equipment software to newer routers or switches during an upgrade. A TFTP server is a small application that is available from a wide variety of developers as freeware for Windows and Linux computers. It’s used to transfer the software onto the newer networking equipment.

TFTP is designed to be a simple, effective, and fast method to upload code to a network device.

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Terminal Emulator Software

Software used to access the device’s command-line interface remotely.

Telnet protocol is rarely used today because it has no security and all data is sent unencrypted; DO NOT USE.

Secure Shell (SSH) is the preferred method of accessing a remote device command line from across a network

The most common open-source emulator is PuTTY, and it supports Telnet, SSH, and serial interfaces. PuTTY is widely used and found in almost every networking shop.

IP Scanners

Can be used for network mapping by listing all of the active IP addresses in each subnet and what applications are running on them. Scanners can tell you what IP addresses are active and what they are “listening for.”

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Command Line Tools

You can use several utilities, both command line and GUI, to verify TCP/IP function on Windows workstations. To meet the Network+ objectives, you'll be required to correctly identify each command's output.

traceart

A command-line utility to help us answer both questions because its output will show us every router interface a TCP/IP packet passes through on the way to its destination.

tracert displays the path a packet takes to get to a remote device in all its glory by using something we call IP packet time to live (TTL).

It's also a handy tool for troubleshooting an internetwork because we can use it to figure out which router along a path through that internetwork happens to be causing a network failure when a certain destination machine or network suddenly becomes unreachable.

This utility is useful if you are having problems reaching a web server on the Internet and you want to know if a wide area network (WAN) link is down or if the server just isn't responding. Start troubleshooting wherever the tracert command stops!

Getting an Asterisk (*) means that the attempt to reach the router took too long and the TTL timed out. Could mean either the router is busy, link is slow, or the network admin disabled it from communicated.

If you are running traceroute and see repeating addresses and TTL time-outs, you probably have a routing loop.

tracert -6 is the command used to tracing packets through IPv6 configured routers.

To use tracert, at a Windows command prompt, type tracert, a space, and the Domain Name Service (DNS) name or IP address of the host machine to which you want to find the route.

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Using ipconfig, ifconfig, and ip

The utilities known as ipconfig (in Windows) and ifconfig/ip (in Unix/Linux/Mac) will display the current configuration of TCP/IP on a given workstation—including the current IP address, DNS configuration, configuration, and default gateway.

There are 2 Local adapters present in the example below: Ethernet Adapter & Wireless LAN Adapter.

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Using the command ipconfig/all

Will show more information including the MAC addresses and the DHCP Lease and DHCP Expire times.

ipconfig/ renew

Used to acquire a new ip address when changing networks or virtual LANs.

When you change networks, you need to get the IP address of that subnet and/or virtual LAN (VLAN). Normally, windows 10 will handle this automatically, but there are times when you’ll have to manually renew the IP configuration when changing networks.

Once this happens, if you’re connected to a DHCP server, you should receive an IP address in the same scheme as the network you’ve just joined.

If entering the command ipconfig/renew doesn’t give you a new IP address, you’ll have to take it a step further. ipconfig /release will need to be entered into the command line as an administrator.

Run command line as an administrator an admin

Type in the command ipconfig /renew

Type in the command ipconfig /release to complete the process of acquiring a new ip address for your host after just joining a new network or VLAN.

Using the ifconfig Utility

Can do everything ipconfig can do, but there a some key differences.

ifconfig is only used in Linux/Unix/Mac operating systems.

ifconfig can also be used to configure a protocol or a particular network interface port.

Looking at this command output below, we can see the following:

It shows the network interface port eth0 running at 10Mbps

ip address of 172.16.0.2

Broadcast address of 172.16.0.255

Subnet Mask of 255.255.255.0

MTU (Max Transmission Unit) size of 1500

MAC address of 00:00:C0:90:B3:42

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Newer versions of the Linux operating system have added the ip utility to replace the ifconfig command. This command serves the same purpose as ifconfig and is used to assign an address to a network interface and/or configure network interface parameters on Linux operating systems.

*Only used in Linux Operations Systems*

The ip command allows us to do the following:

what interfaces are configured on the computer

view and configure their IP values

take an interface up or down

configure routing

display network status information

view and configure multicast values

view the ARP table

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view the host's routing table.

For example, to add the IP address of 192.168.1.1 to interface Ethernet0, use the following command: #ip a add 192.168.1.1/255.255.255.0 dev eth0Using the iptables utility

The iptables firewall utility

A command-line utility built for the Linux operating system that uses what are called chains to allow or disallow traffic. When traffic arrives, iptables looks for a rule that addresses that traffic type, and if none exists, it will enforce the default rule.

There are three different chain types:

Input: Controls behavior for incoming connections

Forward: Used for incoming connections that aren't being delivered locally (like a router would receive)

Output: Used for outgoing connections

You can set the default action to accept, drop, or reject, with the difference between reject and drop being that reject sends an error message back to the source.

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