Meet the Router
Meet the Router Interfaces
Gateway Community College
A router is a computer. Like any computer, we have to get commands and
information into it as well as getting information back out of it. Let’s take a look
at some interfaces on some different Cisco routers.
This is a Cisco 2514 router. Like all routers, we have to provide a keyboard to
type in commands. The console port, located here, allows us to hook up a
personal computer or a dumb terminal. The keyboard and screen of the computer
or terminal become the keyboard and screen of the router. The console port uses
a special rollover or console cable to connect from the computer or terminal to
Located next to the console port, is an auxiliary port, marked AUX. The auxiliary
port allows us to hook up a modem to the router. If we’re not in the same room as
the router, we can dial into the modem that’s attached to the auxiliary port and
enter the user name and password that we’ve set up. We can then type in
commands into a communications program, such as Windows HyperTerminal
and have them transmitted over the phone lines to the router at the other end.
Any information that the router displays in response to these commands is
displayed on the screens of the communications program. Great! Now we have a
way to communicate with the router.
The router is there to do a job – to select the best path to move the packets of data
on the LAN or WAN.
Here are the Ethernet ports of the router. The 2514 has two Ethernet ports
marked AUI 0 and AUI 1. Note that there is an LED, or Light Emitting Diode,
located next to the port. The LED blinks when there is activity on the port.
Different routers may have a different number of Ethernet ports.
The type of connection the Ethernet port uses is called an Attachment Unit
Interface, or AUI. The AUI port allows us to attach a transceiver to it. Ethernet
supports many different types of media, including thin coaxial, thick coaxial,
10Base-T, and fiber-optic.
By using an AUI, which provides a universal connection, we can accommodate
these different media types. We put a transceiver like this one on the AUI. If we
need to change our media type, we simply change the transceiver rather than
having to buy another router.
Ethernet is not the only type of LAN technology supported by routers. You can
buy routers that support FDDI, Token Ring, and other architectures. That takes
care of the Local Area Network, or LAN, connections, so let’s look at the WAN
1-2 Video: Meet the Router Interfaces Copyright 2001, Cisco Systems, Inc.
The WAN, or Wide Area Network, connection lets the router communicate with the
outside world. These WAN connections, or ports, are usually serial connections. The
2514 has two serial ports labeled Serial 0 and Serial 1. And they are located here, next
to the console port.
We connect a V.35 cable like this one to the serial port. The other end of this cable is
connected to a CSU/DSU, which is in turn connected to the service providers WAN
There are other types of WAN ports available like ISDN and ATM. Cisco makes
routers with these types of connections as well.
Let’s take a look at another model of Cisco router, the 1600. The 1600 is physically
smaller than the 2500 router, and is designed to support a smaller number of users.
The 1600 has a console port, but no auxiliary port. The 1600 has an Ethernet AUI port
as well as an Ethernet 10Base-T port that uses an RJ-45 type of connector. Note
however that both the 10Base-T port and the AUI port are labeled Ethernet 0. This
means you can only use one or the other type of connector, but not both at the same
time. Therefore, this particular model of 1600 router has just one functional Ethernet
port at any one time, depending on what type of connection you are using.
Next to it is a serial port marked Serial 0. This uses the same type of V.35 cable to
connect to a CSU/DSU.
The 1600 series has a special modular port located here. It’s called a WAN interface
card, or WIC. The WIC can be purchased in a variety of configurations including 56
Kilobit per second CSU/DSU, T-1 CSU/DSU, Basic Rate Interface ISDN, or another
This modular approach, which is also available in the Cisco 1700, 2600, and 3600
series of routers, allows you to upgrade the WAN connection without replacing the
entire router. To use the WIC port, remove the protective cover, slide the WIC card in,
and secure it in place with the screws.
The 1600 and 2500 routers are considered access layer routers. They connect
workgroups or departmental LANs to a larger network.
Let’s take a look at an example of a distribution layer router, the Cisco 4000.
It still uses IOS, and supports the commands and protocols that you’re learning about in
your class. Let’s take a look at the interfaces on the 4000. Here’s the console port.
Here’s the auxiliary port. This particular Cisco 4000 has two high-speed serial
interface, or HSSI ports, and four Ethernet interfaces.
We typically hook the routers at the distribution layer together with faster LAN and
WAN connectors than we do at the access layer.
At the core layer, we have routers like the Cisco 7000. Core layer routers hook together
distribution layer routers.
The Cisco 7000 is larger, faster, and has more memory than the 4000, but it has many
of the same interfaces. Here’s the console port. Here’s the auxiliary port. And this
particular 7000 router has 24 Ethernet interfaces.
Copyright 2001, Cisco Systems, Inc. Video: Meet the Router Interfaces 1-3
Now that you have seen a variety of Cisco routers, you can see that they have a
lot in common. They all have interfaces that allow us to connect to them as well
as having interfaces for LAN and WAN connections.
1-4 Video: Meet the Router Interfaces Copyright 2001, Cisco Systems, Inc.