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:
  1. Configure terminal emulation software on the PC for:
  2. Connect the RJ-45 connector of the rollover cable to the router console port.
  3. Connect the other end of the rollover cable to the RJ-45 to DB-9 adapter.
  4. Attach the female DB-9 adapter to a PC.