main tasks for ROM are hardware diagnostics during
router bootup and loading the Cisco IOS software from flash to
RAM. Some routers also have a scaled down version of the IOS
that can be used as an alternative boot source. ROMs are not
erasable. They can only be upgraded by replacing the ROM chips
in the sockets. Interfaces – The interfaces are the
router connections to the outside. The three types of
interfaces are local-area network (LANs), wide-area network
(WANs), and Console/AUX. The LAN interfaces are usually one of
several different varieties of Ethernet or Token Ring. These
interfaces have controller chips that provide the logic for
connecting the system to the media. The LAN interfaces may be a
fixed configuration or modular. The WAN interfaces include
serial, ISDN, and integrated Channel Service Unit (CSUs). As
with LAN interfaces, WAN interfaces also have special
controller chips for the interfaces. The WAN interfaces may be
a fixed configuration or modular. The Console/AUX ports are
serial ports used primarily for the initial configuration of
the router. These ports are not networking ports. They are used
for terminal sessions from the communication ports on the
computer or through a modem. Power Supply – The power
supply provides the necessary power to operate the internal
components. Larger routers may use multiple or modular power
supplies. In some of the smaller routers the power supply may
be external to the router. Interactive Media Activity
Drag and Drop: Router Internal Components When the student
completes this activity, the student will be able to define the
internal components of a router. Web Links Maintaining
the Router http://www.cisco.com/en/US/products/hw/
routers/ps259/products_installation_
guide_chapter09186a008007e026.html
Content 1.2
Routers 1.2.2 Router physical characteristics
It is not critical to know the location of the physical
components inside the router to understand how to use the
router. However in some situations, such as adding memory, it
can be very helpful. The exact components used and their
location varies between router models. Figure identifies the
internal components of a 2600 router. Figure shows some of the
external connectors on a 2600 router. Interactive Media
Activity PhotoZoom: Cisco 1721 Router In this PhotoZoom,
the student will view a Cisco 1721 router. Interactive
Media Activity PhotoZoom: Cisco 2621 Router In this
PhotoZoom, the student will view a Cisco 2621 router. Web
Links Hardware Features http://www.cisco.com/en/US/products/
hw/routers/ps259/roducts_installation_ guide_
chapter09186a008007e034.html#xtocid1
Content 1.2
Routers 1.2.3 Router external
connections The three basic types of connections on a
router are LAN interfaces, WAN interfaces, and management
ports. LAN interfaces allow the router to connect to the Local
Area Network media. This is usually some form of Ethernet.
However, it could be some other LAN technology such as Token
Ring or Asynchronous Transfer Mode (ATM). Wide Area Network
connections provide connections through a service provider to a
distant site or to the Internet. These may be serial
connections or any number of other WAN interfaces. With some
types of WAN interfaces, an external device such as a CSU is
required to connect the router to the local connection of the
service provider. With other types of WAN connections, the
router may be directly connected to the service provider. The
function of management ports is different from the other
connections. The LAN and WAN connections provide network
connections through which frame packets are passed. The
management port provides a text-based connection for the
configuration and troubleshooting of the router. The common
management interfaces are the console and auxilliary ports.
These are EIA-232 asynchronous serial ports. They are connected
to a communications port on a computer. The computer must run a
terminal emulation program to provide a text-based session with
the router. Through this session the network administrator can
manage the device. Web Links Module Interface
Information http://www.cisco.com/en/US/products/
hw/routers/ps259/products_installation_guide_
chapter09186a008007e034.html#xtocid2
Content 1.2
Routers 1.2.4 Management port
connections The console port and the auxiliary (AUX) port
are management ports. These asynchronous serial ports are not
designed as networking ports. One of these two ports is
required for the initial configuration of the router. The
console port is recommended for this initial configuration. Not
all routers have an auxiliary port. When the router is first
put into service, there are no networking parameters
configured. Therefore the router cannot communicate with any
network. To prepare for initial startup and configuration,
attach an RS-232 ASCII terminal, or a computer emulating an
ASCII terminal, to the system console port. Then configuration
commands can be entered to set up the router. Once this initial
configuration is entered into the router through the console or
auxiliary port, the router can then be connected to the network
for troubleshooting or monitoring. The router can also be
configured from a remote location by dialing to a modem
connected to the console or auxiliary port on the router. The
console port is also preferred over the auxiliary port for
troubleshooting. This is because it displays router startup,
debugging, and error messages by default. The console port can
also be used when the networking services have not been started
or have failed. Therefore, the console port can be used for
disaster and password recovery procedures. Web Links
Connecting the DC Power Supply http://www.cisco.com/en/US/products/
hw/routers/ps259/products_installation_guide_
chapter09186a008007dff8.html#xtocid14
Content 1.2
Routers 1.2.5 Connecting console
interfaces The console port is a management port used to
provide out-of-band access to the router. It is used for the
initial configuration of the router, monitoring, and disaster
recovery procedures. To connect to the console port, a rollover
cable and a RJ-45 to DB-9 adapter are used to connect a PC.
Cisco supplies the necessary adapter to connect to the console
port. The PC or terminal must support VT100 terminal emulation.
Terminal emulation software such as HyperTerminal is usually
used. To connect the PC to a router: - Configure
terminal emulation software on the PC for:
- The
appropriate com port
- 9600 baud
- 8 data
bits
- No parity
- 1 stop bit
- No flow
control
- Connect the RJ-45 connector of the
rollover cable to the router console port.
- Connect
the other end of the rollover cable to the RJ-45 to DB-9
adapter.
- Attach the female DB-9 adapter to a PC.