What is a Router?

A router is a device that receives and sends data on computer networks. Routers are sometimes confused with network hubs, modems, or network switches. However, routers can combine the functions of these components, and connect with these devices, to improve Internet access or help create business networks.

How does a router work?

Cisco guide and direct network data, using packets that contain various kinds of data—such as files, communications, and simple transmissions like web interactions.

The data packets have several layers, or sections, one of which carries identifying information such as sender, data type, size, and most importantly, the destination IP (Internet protocol) address. The router reads this layer, prioritizes the data, and chooses the best route to use for each transmission.

How do routers help your business?

A common tool for modern network computing, routers connect employees to networks, both local and the Internet, where just about every essential business activity takes place. Without routers, we wouldn’t be able to use the Internet to collaborate, communicate, or gather information and learn. 

Routers can also provide security. Embedded firewall and content filtering software provide an additional protection from unwanted content and malicious websites without affecting your online experience.

A router isn’t just for data transmission or Internet connections, though. Most routers allow you to connect hard drives and use them as file-sharing servers, or printers that can then be accessed by anyone on the network.

Types of routers

Core router

Core routers are generally used by service providers (i.e. AT&T, Verizon, Vodafone) or cloud providers (i.e. Google, Amazon, Microsoft). They provide maximum bandwidth to connect additional routers or switches. Most small businesses will not need core routers. But very large enterprises that have many employees working in various buildings or locations may use core routers as part of their network architecture.

Edge router

An edge router, also called a gateway router or just “gateway” for short, is a network’s outermost point of connection with external networks, including the Internet.

Edge routers are optimized for bandwidth and designed to connect to other routers to distribute data to end users. Edge routers don’t usually offer Wi-Fi or the ability to manage local networks fully. They typically have only Ethernet ports—an input to connect to the Internet and several outputs to connect additional routers.

Edge router and modem are somewhat interchangeable terms, though the latter term is no longer commonly used by manufacturers or IT professionals when referencing edge routers.

Distribution router

A distribution router, or interior router, receives data from the edge router (or gateway) via a wired connection and sends it on to end users, typically via Wi-Fi, though the router usually also includes physical (Ethernet) connections for connecting users or additional routers.

Wireless router

Wireless routers, or residential gateways, combine the functions of edge routers and distribution routers. These are commonplace routers for home networks and Internet access.

Most service providers provide full-featured wireless routers as standard equipment. But even if you have the option to use an ISP’s wireless router in your small business, you may want to use a business-level router to take advantage of better wireless performance, more connectivity controls, and security.

Virtual router

Virtual routers are pieces of software that allow some router functions to be virtualized in the cloud and delivered as a service. These routers are ideal for large businesses with complex network needs. They offer flexibility, easy scalability, and a lower entry cost. Another benefit of virtual routers is reduced management of local network hardware.

In this lab, we’ll learn how to configure a Cisco SG300 switch/router to do layer-2 vlan switching between multiple Ethernet interfaces.

Set up three machines

0. Boot your 3 machines into Linux. Unplug 2 of the machines from all networks.

1. Get a Cisco SG300 switch/router and serial-to-USB cable from your benevolent professor. Connect the switch/router to a USB port on the one machine still connected to the orange network. Plug in the router now so that it starts booting.

2. Download and install putty on the same machine. (Use apt-get. If you don’t remember how to do this, look back at a previous lab to see how.)

*** Q1: What is the command to get putty onto your computer? ***

3. Configure putty to be able to communicate with the router over the USB port (/dev/ttyUSB0).

• run sudo putty
• Click on Serial for the Connection Type:
• Set the serial line to /dev/ttyUSB0
• Click on Keyboard, then set backspace key to Control-H.
• Click on Session. Click on Default Settings. Click Save.
• Click Open.

4. Login

• Hit Enter a few times. You should eventually see: (Your responses are in bold.)

User Name: cisco
Password: cisco

Please change your password from the default settings. Please change the password for better protection of your network. Do you want to change the password (Y/N)[Y] ? N

switch4968b6#

5. Set some initial configuration options

switch4968b6# config terminal (set the device to receive configuration commands from the terminal)switch4968b6(config)# hostname is333-1 (or, better, choose your own name here)
is333-1# end
is333-1# show running-config

<lots of output here>

*** Q2. What mode is the switch in? What version of software is running? ***

6. Let’s create a new VLAN to do switching on

is333-1# config t
is333-1(config)# vlan database
is333-1(config-vlan)# vlan 10
is333-1(config-vlan)# int vlan 10
is333-1(config-if)# name red (or pick your own name here)
is333-1(config-vlan)# end
is333-1# show run

7. Now, we can add physical ports/interfaces to the VLAN

First, plug your other two computers into the switch/router in ports 1 and 2. Make sure you see the green carrier LEDs flash periodically. Then, do the following:

is333-1# config t
is333-1(config)# int Gi1 (short for GigabitEthernet 1)
is333-1(config-if)# switchport mode access
is333-1(config-if)# switchport access vlan 10
is333-1(config-if)# end
is333-1# show vlan

Repeat step 7. for port Gi2. Then, do the following to save the current configuration to flash so that it is used after a reboot.

is333-1# copy running-config startup-config

8. Configuring IP addresses on the other machines

We don’t have a DHCP server running anywhere, so we’ll have to configure IP addresses on these machines “statically”.

• From the top launch bar, click on the Networking icon and do Edit.
• Select Wired Connection 1, and click Edit...
• Select IPv4 Settings tab. Change the Method: to Manual.
• Click +Add
• Enter 192.168.10.10, <tab>, 192.168.10.1.
• Click Save...
• In a terminal window, run ip addr and confirm that the machine has the IP address configured.
• Repeat on the other machine (using a different IP address, on the 192.168.10 network).
• Run ping between the machines to see if you can communicate.

9. Monitor the behavior

On the switch/router, run this command:

• show mac address-table

*** Q3. What does it tell you? ***

• Unplug one of the machines.
  *** Q4. What output do you see printed on the console? ***
• Run show mac address-table again.
  *** Q5. What changed? ***
• Run show spanning-tree
  *** Q6. Describe some of the interesting information you see. ***

10. Access the switch from a browser

In order to access the web interface on the switch, we have to give the switch itself an IP address, and then we have to get onto that same network from another computer.

On the switch, do these commands:

is333-1# config t
is333-1(config)# int vlan 1 (we are configuring the management vlan, vlan 1)
is333-1(config-if)# ip address 192.168.1.1 /24
is333-1# end

*** Q7. Describe what the above commands did. ***

Now, on the Linux machine that you’ve been using to type commands into the switch/router console:

• Remove the machine from the orange network.
• Connect the machine via ethernet to the switch.
• Configure the machine’s ethernet interface to use a manual IP address, which you set to 192.168.1.2, with the gateway being 192.168.1.1.

Open a browser on the Linux box and go to 192.168.1.1. Use cisco for the username, and cisco for the password.

Now, poke around a bit on the web interface. Look at statistics for the interfaces, vlan information, etc.

*** Q8. Describe how you can view the system log and describe what you see in that log. ***

*** Q9. Describe how you can change one of the ports being used (port 1 or 2) to be “Administratively Down”. ***

11. Clean up and submit your answers via moodle.

• via the console window, reset the switch/router back to default factory mode:
• delete startup-config
• reload

Clean up your ethernet cables nicely and put them away.

On each machine change the interfaces back to using DHCP (Automatic) from Manual IP address configuration. Plug the machines back in to the orange network and confirm that they get 153.106.x.y IP addresses.

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