Router Startup and Configuration

Transcription

1 Router Startup and Configuration

2 Router Startup In general, the boot process follows these steps: Test hardware (POST) Load the bootstrap program Locate and load the Cisco IOS Locate and load the router configuration file 2

3 3

4 Test Hardware (POST) Read-only memory (ROM) in a router Typically contains the power-on self-test (POST), the bootstrap program, and often a version of the operating system POST is a diagnostic test that determines if the hardware is operating correctly During the POST, the bootstrap program, also called the ROM Monitor, checks basic operations of the attached hardware The ROM Monitor checks the configuration register for instructions regarding how to load the Cisco IOS 4

5 Router Configuration Files startup-config The router configuration file that loads during the boot process Sometimes referred to as the backup configuration Because it is the saved version of the configuration file To revert to the settings in your startup-config Reboot the system by powering the router off and back on again or Issue the reload command at the privileged EXEC mode prompt 5

6 Router Configuration Files (continued) Note that when you copy over the startup configuration in NVRAM, that file is replaced When you copy to the running configuration in RAM, the configuration files are blended To view the contents of the startup-config Type show startu-pconfig or just show start at the enable prompt To see your working or running configuration Type show running-config or just show run at the enable prompt 6

7 7

8 Methods for Making Changes You can usually implement and test changes without saving them to the startup configuration Basic steps to implement changes: Make changes as desired to the configuration Examine those changes Determine if the changes meet the desired result Remove the changes if they do not meet the desired result, or simply reboot the router Copy the changes from the running configuration to the startup configuration when they do meet the desired result 8

9 IP on the Router To manually configure IP on an interface You must first change to interface configuration mode Then, you can use the ip address command to configure an IP address for the specific interface In the event you are configuring a serial interface as a DCE (data communication equipment) You will also need to add the clockrate [bandwidth in bits per second] command 9

10 IP Connectivity 10

11 Telnet Telnet Utility that connects at the highest layer of the OSI model and provides remote access to other devices Cisco routers allow telnet connections via their virtual terminal ports If you can establish telnet connectivity to a router It is available on the network and you have connectivity at all layers 11

12 IP Host Names Sometimes, you cannot gain connectivity because the host name that you are trying to connect with is entered in a table incorrectly To determine the address to name mapping on your router, type: router#show hosts To add an entry to your hosts file for name resolution Go to global configuration mode and type: router(config)#ip host router CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 12

13 IP Host Names (continued) To remove that entry, type: router(config)#no ip host router To allow a name server to handle the IP address to name resolution, type: router(config)#ip name-server

14 Ping and Trace Ping and Trace verify connectivity at the Internetwork layer of the TCP/IP model Ping can return the following replies:! Successful receipt of the ICMP echo. Request timed out U C I Destination was unreachable Congestion experienced Ping interrupted? Packet type unknown & Packet TTL exceeded 14

15 Ping and Trace (continued) Using the ping command alone Referred to as extended mode ping Allows you to enter your ping command step by step Trace sends multiple ICMP packets with progressively higher time-to-live counters (TTL) Until the packet reaches the destination 15

16 Ping and Trace (continued) The following responses can be returned by a trace:!h Indicates that a router received, but did not forward, the ICMP echo request P N U Protocol unreachable Network unreachable Port unreachable * Request timed out 16

17 IP Route If you cannot get connectivity using Ping or Trace, you should check your routing table Issue the show ip route command from the enable mode prompt To display the routing table Typically, routing tables are dynamically created when routing protocols are configured on the router If you want, you can use the ip route command from the global configuration mode To statically enter routes in the routing table 17

18 Checking the Interface show interfaces command Check the configuration of a specific interface from the enable mode prompt Example: router#show int s0/0 Replies Serial0/0 is up, line protocol is up Serial0/0 is up, line protocol is down Serial0/0 is up, line protocol is administratively down Serial0/0 is down, line protocol is down 18

19 19

20 Checking the Interface (continued) Clear counters The router keeps detailed statistics regarding data passing across its interfaces To clear the counters for interface f0/0, type: router#clear interface f0/0 debug command One of the most powerful tools you can use to obtain information from your router Tool is only available from privileged EXEC mode Debug has numerous subcommands 20

21 21

22 CDP Cisco Discovery Protocol (CDP) Cisco proprietary Data Link layer protocol Shares configuration information between Cisco devices that are connected directly to each other All Cisco devices can use CDP to: Discover each other Learn about the configurations of other devices Using CDP can help you quickly determine the network topology CDP was designed to be a low-overhead protocol 22

23 CDP (continued) 23

24 Cisco IOS Cisco IOS is usually loaded from flash memory If the router cannot find the IOS in flash memory, it will look for a copy on a TFTP server If it cannot find one there, it will boot a minimal version of the IOS from ROM If you want to see information about your router s flash memory: Type show flash from the enable mode prompt 24

25 25

26 Cisco IOS (continued) 26

27 Configuration Register Every Cisco router has a 16-bit configuration register, which is stored in NVRAM This register allows you to control several boot functions: Forcing the system into the bootstrap program Enabling or disabling the console Break function Setting the console terminal baud rate Loading the IOS from ROM Loading the IOS from a TFTP server Examine the configuration register by typing show version 27

28 28

29 Configuration Register (continued) 29

30 ROM Monitor Mode ROM Monitor mode The bootstrap program that is built into the firmware of the router Used to initialize the hardware and load the IOS ROM Monitor can be used to perform other tasks such as diagnostics and recovering passwords Configure your system to enter ROM Monitor mode Enter the following command at the global configuration prompt: router(config)#config-register 0x

31 ROM Monitor Mode (continued) Configure your system to boot a smaller IOS image from ROM and enter RxBoot mode Enter the following command at the global configuration prompt: router(config)#config-register 0x

32 RxBoot Mode RxBoot mode A limited version of the IOS Entering RxBoot mode is often done intentionally When you want to access a TFTP server to download a new IOS If your router enters RxBoot mode without your intervention Indicates that the router could not find a good IOS image Prompt: router(boot) 32

33 Boot System Commands As long as the configuration register is configured with a 2 as the final hexadecimal digit The ROM Monitor will look for boot system commands in NVRAM during the bootup process Enable your system to boot an IOS file from the TFTP server Issue the following command from global configuration mode: router(config)#boot system tftp somefile.bin 33

34 Backing Up and Restoring the IOS copy flash tftp The command for backing up your IOS to a TFTP server You will be asked for the source filename, the IP address of the TFTP server, and the destination filename Type erase flash at the privileged EXEC mode prompt To erase the IOS 34

35 35

36 Upgrading the IOS Before you load a new IOS file to your router Use the show flash command to ensure there is enough free memory to hold it The system will tell you how much memory is used and how much is free If there is not enough memory to hold both the current IOS image and the upgrade You will have to erase the existing flash memory as previously mentioned 36

37 Router Password Recovery Password recovery Process that allows you to get into the router without the necessary passwords You must be physically connected to the router using the console cable Steps to perform password recovery on the Cisco 2600 series: Connect to the router from a PC using the console port and the HyperTerminal program Enter the show version command and record the value of the configuration register 37

38 Router Password Recovery (continued) Steps to perform password recovery on the Cisco 2600 series: (continued) Turn the router off and on using the power switch Press Ctrl+Break several times within the first 60 seconds of bootup At the rommon 1> prompt, type confreg 0x2142 and press Enter Enter the reset command at the rommon 2> prompt Enter no if asked to enter the system configuration dialog Enter enable to get to privileged mode 38

39 Router Password Recovery (continued) Steps to perform password recovery on the Cisco 2600 series: (continued) Enter the copy start run command to load the saved configuration file from NVRAM into RAM Enter the show run command to view the configuration To change the enable secret command, enter the following commands: Router#config t Router(config)#enable secret [secret password] 39

40 Router Password Recovery (continued) Steps to perform password recovery on the Cisco 2600 series: (continued) Enter config-register 0x2102 at the global configuration mode prompt to make sure the router reboots in the default manner Enter the copy run start command to save your changes 40

41 Security Device Manager Security Device Manager (SDM) A Web-based tool primarily used for implementing and testing security configurations Commonly used to configure routing protocols, WAN services, wireless routing, firewalls, virtual private networks (VPNs), and quality of service (QoS) SDM is typically not used to configure basic functionality on a Cisco router In fact, SDM cannot do all things 41

42 42