C H A P T E R 13 Operating Cisco Routers Routers differ from switches in terms of their core purposes. Switches forward Ethernet frames by comparing the frame’s destination MAC address to the switch’s MAC address table, whereas routers forward packets by comparing the destination IP address to the router’s IP routing table. Ethernet switches today typically have only one or more types of Ethernet interfaces, whereas routers have Ethernet interfaces, serial WAN interfaces, and other interfaces with which to connect via cable and digital subscriber line (DSL) to the Internet. Routers understand how to forward data to devices connected to these different types of interfaces, whereas Ethernet switches focus solely on forwarding Ethernet frames to Ethernet devices. So, while both switches and routers forward data, the details of what can be forwarded, and to what devices, differ significantly. Even though their core purposes differ, Cisco routers and switches use the same CLI. This chapter covers the CLI features on routers that differ from the features on switches, particularly features that differ from the switch CLI features as covered in Chapter 8. This chapter also explains more details about the physical installation of Cisco routers, along with some details about how routers choose and load IOS. “Do I Know This Already?” Quiz The “Do I Know This Already?” quiz allows you to assess if you should read the entire chapter. If you miss no more than one of these nine self-assessment questions, you might want to move ahead to the “Exam Preparation Tasks” section. Table 13-1 lists the major headings in this chapter and the “Do I Know This Already?” quiz questions covering the material in those headings so you can assess your knowledge of these specific areas. The answers to the “Do I Know This Already?” quiz appear in Appendix A. Table 13-1 “Do I Know This Already?” Foundation Topics Section-to-Question Mapping Foundation Topics Section Questions Installing Cisco Routers 1, 2 Cisco Router IOS CLI 3–7 Upgrading Cisco IOS Software and the Cisco IOS Software Boot Process 8, 9 1828xbook.fm Page 399 Thursday, July 26, 2007 3:10 PM 400 Chapter 13: Operating Cisco Routers 1. Which of the following installation steps are typically required on a Cisco router, but not typically required on a Cisco switch? a. Connect Ethernet cables b. Connect serial cables c. Connect to the console port d. Connect the power cable e. Turn the on/off switch to “on” 2. Which of the following roles does a SOHO router typically play in regards to IP address assignment? a. DHCP server on the interface connected to the ISP b. DHCP server on the interface connected to the PCs at the home/office c. DHCP client on the interface connected to the ISP d. DHCP client on the interface connected to the PCs at the home/office 3. Which of the following features would you typically expect to be associated with the router CLI, but not with the switch CLI? a. The clock rate command b. The ip address address mask command c. The ip address dhcp command d. The interface vlan 1 command 4. You just bought two Cisco routers for use in a lab, connecting each router to a different LAN switch with their Fa0/0 interfaces. You also connected the two routers’ serial interfaces using a back-to-back cable. Which of the following steps is not required to be able to forward IP on both routers’ interfaces? a. Configuring an IP address on each router’s FastEthernet and serial interfaces b. Configuring the bandwidth command on one router’s serial interface c. Configuring the clock rate command on one router’s serial interface d. Setting the interface description on both the FastEthernet and serial interface of each router 1828xbook.fm Page 400 Thursday, July 26, 2007 3:10 PM “Do I Know This Already?” Quiz 401 5. The output of the show ip interface brief command on R1 lists interface status codes of “down” and “down” for interface Serial 0/0. Which of the following could be true? a. The shutdown command is currently configured for that interface. b. R1’s serial interface has been configured to use Frame Relay, but the router on the other end of the serial link has been configured to use PPP. c. R1’s serial interface does not have a serial cable installed. d. Both routers have been cabled to a working serial link (CSU/DSUs included), but only one router has been configured with an IP address. 6. Which of the following commands does not list the IP address and mask of at least one interface? a. show running-config b. show protocols type number c. show ip interface brief d. show interfaces e. show version 7. Which of the following is different on the Cisco switch CLI as compared with the Cisco router CLI? a. The commands used to configure simple password checking for the console b. The number of IP addresses configured c. The types of questions asked in setup mode d. The configuration of the device’s host name e. The configuration of an interface description 8. Which of the following could cause a router to change the IOS that is loaded when the router boots? a. reload EXEC command b. boot EXEC command c. reboot EXEC command d. boot system configuration command e. reboot system configuration command f. configuration register 1828xbook.fm Page 401 Thursday, July 26, 2007 3:10 PM 402 Chapter 13: Operating Cisco Routers 9. Which of the following hexadecimal values in the last nibble of the configuration register would cause a router to not look in Flash memory for an IOS? a. 0 b. 2 c. 4 d. 5 e. 6 1828xbook.fm Page 402 Thursday, July 26, 2007 3:10 PM Installing Cisco Routers 403 Foundation Topics Installing Cisco Routers Routers collectively provide the main feature of the network layer—the capability to forward packets end-to-end through a network. As introduced in Chapter 5, “Fundamentals of IP Addressing and Routing,” routers forward packets by connecting to various physical network links, like Ethernet, serial links, and Frame Relay, and then using Layer 3 routing logic to choose where to forward each packet. As a reminder, Chapter 3, “Fundamentals of LANs,” covered the details of making those physical connections to Ethernet networks, while Chapter 4, “Fundamentals of WANs,” covered the basics of cabling with WAN links. This section examines some of the details of router installation and cabling, first from the enterprise perspective, and then from the perspective of connecting a typical small office/home office (SOHO) to an ISP using high-speed Internet. Installing Enterprise Routers A typical enterprise network has a few centralized sites as well as lots of smaller remote sites. To support devices at each site (the computers, IP phones, printers, and other devices), the network includes at least one LAN switch at each site. Additionally, each site has a router, which connects to the LAN switch and to some WAN link. The WAN link provides connectivity from each remote site, back to the central site, and to other sites via the connection to the central site. Figure 13-1 shows one way to draw part of an enterprise network. The figure shows a typical branch office on the left, with a router, some end-user PCs, and a nondescript generic drawing of an Ethernet. The central site, on the right, has basically the same components, with a point-to-point serial link connecting the two routers. The central site includes a server farm with two servers, with one of the main purposes of this internetwork being to provide remote offices with access to the data stored on these servers. Figure 13-1 purposefully omits several details to show the basic concepts. Figure 13-2 shows the same network, but now with more detail about the cabling used at each site. 1828xbook.fm Page 403 Thursday, July 26, 2007 3:10 PM 404 Chapter 13: Operating Cisco Routers Figure 13-1 Generic Enterprise Network Diagram Figure 13-2 More Detailed Cabling Diagram for the Same Enterprise Network Figure 13-2 shows the types of LAN cables (UTP), with a couple of different WAN cables. The LAN connections all use UTP straight-through cabling pinouts, except for the UTP cable between the two switches, which is a crossover cable. The serial link in the figure shows the two main options for where the channel service unit/ digital service unit (CSU/DSU) hardware resides: either outside the router (as shown at the branch office in this case) or integrated into the router’s serial interface (as shown at the PC4 PC5 PC1 PC2 PC3 PC6 S1 S2 R1 R2 Branch Office Central Site Servers End Users S1 S2 PC4 PC5 PC1 PC2 PC3 PC6 R1 R2 Branch Office Central Site Leased Line UTP Cables UTP Cables UTP (Crossover) Servers Serial Interface With Integrated CSU/DSU Serial CableUTP Cables CSU/ DSU IP 1828xbook.fm Page 404 Thursday, July 26, 2007 3:10 PM Installing Cisco Routers 405 central site). Most new installations today include the CSU/DSU in the router’s serial interface. The WAN cable installed by the telco typically has an RJ-48 connector, which is the same size and shape as an RJ-45 connector. The telco cable with the RJ-48 connector inserts into the CSU/DSU, meaning it connects directly into the central site router in this case, but into the external CSU/DSU at the branch office router. At the branch, the external CSU/DSU would then be cabled, using a serial cable, to the branch router’s serial port. (See Figure 4-4 in Chapter 4 for a reminder of WAN serial cables.) Cisco Integrated Services Routers Product vendors, including Cisco, typically provide several different types of router hardware, including some routers that just do routing, with other routers that serve other functions in addition to routing. A typical enterprise branch office needs a router for WAN/ LAN connectivity, and a LAN switch to provide a high-performance local network and connectivity into the router and WAN. Many branches also need Voice over IP (VoIP) services, and several security services as well. (One popular security service, virtual private networking (VPN), is covered in Chapter 6, “Fundamentals of TCP/IP Transport, Applications, and Security.”) Rather than require multiple separate devices at one site, as shown in Figure 13-2, Cisco offers single devices that act as both router and switch, and provide other functions as well. Following that concept further, Cisco offers several router model series in which the routers support many other functions. In fact, Cisco has several router product series called Integrated Services Routers (ISR), with the name emphasizing the fact that many functions are integrated into a single device. If you have not seen Cisco routers before, you can go to http://www.cisco.com/go/isr and click any of the 3D Product Demonstration links to see interactive views of a variety of Cisco ISR routers. However, for the sake of learning and understanding the different functions, the CCNA exams focus on using a separate switch and separate router, which provides a much cleaner path for learning the basics. Figure 13-3 shows a couple of pictures taken from the interactive demo of the Cisco 1841 ISR, with some of the more important features highlighted. The top part of the figure shows a full view of the back of the router. It also shows a magnified view of the back of the router, with a clearer view of the two FastEthernet interfaces, the console and auxiliary ports, and a serial card with an internal CSU/DSU. (You can find the interactive demo from which these photos were taken at the same ISR web page mentioned in the previous paragraph.) 1828xbook.fm Page 405 Thursday, July 26, 2007 3:10 PM 406 Chapter 13: Operating Cisco Routers Figure 13-3 Photos of a Model 1841 Cisco Integrated Services Router (ISR) Physical Installation Armed with the planning information shown in Figure 13-2, and the perspectives shown in Figure 13-3, you can physically install a router. To install a router, follow these steps: Step 1 Connect any LAN cables to the LAN ports. Step 2 If using an external CSU/DSU, connect the router’s serial interface to the CSU/DSU, and the CSU/DSU to the line from the telco. Step 3 If using an internal CSU/DSU, connect the router’s serial interface to the line from the telco. Step 4 Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router. Step 5 Connect a power cable from a power outlet to the power port on the router. Step 6 Turn on the router. Note that the steps generally follow the same steps used for installation of LAN switches— install the cables for the interfaces, connect the console (as needed), and connect the power. However, note that most of the Cisco Catalyst switches do not have a power on/off switch— once the switch is connected to power, the switch is on. However, Cisco routers do have on/ off switches. On/Off Switch Console Aux Serial Interface with Integrated CSU/DSU Two FastEthernet Interfaces Additional Modular Interface Card Power Socket 1828xbook.fm Page 406 Thursday, July 26, 2007 3:10 PM Installing Cisco Routers 407 Installing Internet Access Routers Routers play a key role in SOHO networks, connecting the LAN-attached end-user devices to a high-speed Internet access service. Once connected to the Internet, SOHO users can send packets to and from their enterprise network at their company or school. As in the enterprise networking market, product vendors tend to sell integrated networking devices that perform many functions. However, in keeping with the CCNA strategy of understanding each function separately, this section first examines the various networking functions needed at a typical SOHO network, using a separate device for each function. Following that, a more realistic example is shown, with the functions combined into a single device. A SOHO Installation with a Separate Switch, Router, and Cable Modem Figure 13-4 shows an example of the devices and cables used in a SOHO network to connect to the Internet using cable TV (CATV) as the high-speed Internet service. For now, keep in mind that the figure shows one alternative for the devices and cables, whereas many variations are possible. Figure 13-4 Devices in a SOHO Network with High-Speed CATV Internet This figure has many similarities to Figure 13-2, which shows a typical enterprise branch office. The end-user PCs still connect to a switch, and the switch still connects to a router’s Ethernet interface. The router still provides routing services, forwarding IP packets. The voice details differ slightly between Figure 13-2 and Figure 13-4, mainly because PC1 PC1 CATV Cable Cable Modem PC1 PC2 R1 ISP/Internet UTP Cables UTP Cable Ethernet Interfaces UTP Cables Wireless SOHO Phone Cable Voice Adapter 1828xbook.fm Page 407 Thursday, July 26, 2007 3:10 PM 408 Chapter 13: Operating Cisco Routers Figure 13-4 shows a typical home-based Internet phone service, which uses a normal analog phone and a voice adapter to convert from analog voice to IP. The main differences between the SOHO connection in Figure 13-4 and the enterprise branch in Figure 13-2 relate to the connection into the Internet. An Internet connection that uses CATV or DSL needs a device that converts between the Layer 1 and 2 standards used on the CATV cable or DSL line, and the Ethernet used by the router. These devices, commonly called cable modems and DSL modems, respectively, convert electrical signals between an Ethernet cable and either CATV or DSL. In fact, while the details differ greatly, the purpose of the cable modem and DSL modem is similar to a CSU/DSU on a serial link. A CSU/DSU converts between the Layer 1 standards used on a telco’s WAN circuit and a serial cable’s Layer 1 standards—and routers can use serial cables. Similarly, a cable modem converts between CATV signals and a Layer 1 (and Layer 2) standard usable by a router—namely, Ethernet. Similarly, DSL modems convert between the DSL signals over a home telephone line and Ethernet. To physically install a SOHO network with the devices shown in Figure 13-4, you basically need the correct UTP cables for the Ethernet connections, and either the CATV cable (for cable Internet services) or a phone line (for DSL services). Note that the router used in Figure 13-4 simply needs to have two Ethernet interfaces—one to connect to the LAN switch, and one to connect to the cable modem. Thinking specifically just about the router installation, you would need to use the following steps to install this SOHO router: Step 1 Connect a UTP straight-through cable from the router to the switch. Step 2 Connect a UTP straight-through cable from the router to the cable modem. Step 3 Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router. Step 4 Connect a power cable from a power outlet to the power port on the router. Step 5 Turn on the router. A SOHO Installation with an Integrated Switch, Router, and DSL Modem Today, most new SOHO installations use an integrated device rather than the separate devices shown in Figure 13-4. In fact, you can buy SOHO devices today that include all of these functions: ■ Router ■ Switch ■ Cable or DSL modem 1828xbook.fm Page 408 Thursday, July 26, 2007 3:10 PM [...]... Source file name? c4500-d-mz.12 0-5 .bin Destination file name [c4500-d-mz.12 0-5 .bin]? Accessing file c4500-d-mz.12 0-5 .bin ‘ on 134 .141.3.33 Loading c4500-d-mz.12 0-5 .bin from 134 .141.3.33 (via Ethernet0): ! [OK] Erase flash device before writing? [confirm] Flash contains files Are you sure you want to erase? [confirm] Copy ‘c4500-d-mz.12 0-5 .bin ‘ from server y as ‘c4500-d-mz.12 0-5 .bin ‘ into Flash WITH... verify the contents of Flash memory, as demonstrated in Example 1 3-6 (The show flash output can vary among router families Example 1 3-6 is output from a 2500 series router.) Example 1 3-6 Verifying Flash Memory Contents with the show flash Command s fred#show flash System flash directory: File 1 Length 133 05352 Name/status c2500-ds-l.12 2-1 .bin [133 05416 bytes used, 3471800 available, 16777216 total] 16384K... simply use the ip address address mask interface subcommand Example 1 3-2 shows an example configuration of IP addresses on two router interfaces, and the resulting differences in the show ip interface brief and show interfaces commands from Example 1 3-1 (No IP addresses were configured when the output in Example 1 3-1 was gathered.) Example 1 3-2 Configuring IP Addresses on Cisco Routers c Albuquerque#configure... other router Example 1 3-3 shows an example configuration for a router named Albuquerque, with a couple of important commands related to WAN links NOTE Example 1 3-3 omits some of the output of the show running-config command, specifically the parts that do not matter to the information covered here Example 1 3-3 Albuquerque Router Configuration with clock rate Command s Albuquerque#show running-config ! lines... link is actually created with cabling in a lab The lab networks used to build the examples in this book, and probably in any labs engineers use to do proof-of-concept testing, or even labs you use in CCNA classes, use back-to-back serial cables (see the Chapter 4 section “Building a WAN Link in a Lab” for a reminder) Back-to-back WAN connections do not use a CSU/DSU, so one router must supply the clocking,... feature has been around a long time and is a more likely topic for the exams Figure 1 3-6 Complete Cisco IOS Software Upgrade Process www.cisco.com Internet FTP/HTTP (Any Convenient Method) TFTP Server Copy tftp flash 421 1828xbook.fm Page 422 Thursday, July 26, 2007 3:10 PM 422 Chapter 13: Operating Cisco Routers Example 1 3-5 provides an example of the final step, copying the IOS image into Flash memory... future setting (if different) Example 1 3-7 demonstrates output from the show version command, highlighting the key pieces of information Note that the preceding list is in the same order in which the highlighted information appears in the example Example 1 3-7 show version Command Output s Albuquerque#show version Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(9)T, RELEASE... Copyright (c) 198 6-2 006 by Cisco Systems, Inc continues 429 1828xbook.fm Page 430 Thursday, July 26, 2007 3:10 PM 430 Chapter 13: Operating Cisco Routers Example 1 3-7 show version Command Output (Continued) Compiled Fri 16-Jun-06 21:26 by prod_rel_team ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1) Albuquerque uptime is 5 hours, 20 minutes System returned to ROM by reload at 13: 12:26 UTC... July 26, 2007 3:10 PM Cisco Router IOS CLI ■ Voice Adapter ■ Wireless AP ■ Hardware-enabled encryption The CCNA exams do indeed focus on separate devices to aid the learning process However, a newly installed high-speed SOHO Internet connection today probably looks more like Figure 1 3-5 , with an integrated device Figure 1 3-5 SOHO Network, Using Cable Internet and an Integrated Device Integrated Device... complete, Example 1 3-4 demonstrates the use of setup mode If you do not have a router with which to practice setup mode, take the time to review the example, and see the kinds of information requested in the various questions NOTE The questions asked, and the default answers, differ on some routers in part due to the IOS revision, feature set, and router model Example 1 3-4 Router Setup Configuration Mode - . 3:10 PM 404 Chapter 13: Operating Cisco Routers Figure 1 3-1 Generic Enterprise Network Diagram Figure 1 3-2 More Detailed Cabling Diagram for the Same Enterprise Network Figure 1 3-2 shows the. on many commands, for example, show interfaces type number, to see details for just that interface. Example 1 3-1 shows sample output from these three commands. Example 1 3-1 Listing the Interfaces. build the examples in this book, and probably in any labs engineers use to do proof-of-concept testing, or even labs you use in CCNA classes, use back-to-back serial cables (see the Chapter 4