Chapter 5: Managing a Cisco Internetwork Sybex CCNA 640-802 Chapter 5: Managing a Cisco Internetwork

Chapter 5 Objectives Cisco Router Components Boot Sequence Configuration register Backing up and restoring the IOS Backing up and restoring the configuration Cisco Discovery Protocol Telnet Resolving hostnames Troubleshooting tools 2

Cisco Router Components Bootstrap Brings up the router during initialization POST Checks basic functionality; hardware & interfaces ROM monitor Manufacturing testing & troubleshooting Mini-IOS Loads Cisco IOS into flash memory RAM Holds packet buffers, routing tables, & software Stores running-config

Cisco Router Components (cont) ROM Starts & maintains the router Flash Memory Holds Cisco IOS Not erased when the router is reloaded NVRAM Holds router (& switch) configurations (startup-config) Configuration Register Controls how the router boots up

Boot Sequence 1: Router performs a POST 2: Bootstrap looks for & loads the Cisco IOS 3: IOS software looks for a valid configuration file 4: Startup-config file (from NVRAM) is loaded If startup-config file is not found, the router will start the setup mode

Configuration Registers 16-bit software written into NVRAM Loads from flash memory & looks for the startup-config file Configuration Register Bits 16 bits read 15-0, from left to right default setting: 0x2102 Register 2 1 0 2 , Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Binary 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 NOTE: 0x means the digits that follow are in hexadecimal You read the numbers in the “Binary” (lower) line above as four groups of four bits each. Each group reads across: “8 4 2 1”, so in the binary line, the groups are: 0 0 1 0 = 2, 0 0 0 1 = 1, 0 0 0 0 = 0, and 0 0 1 0 = 2 The entire row, therefore, reads “2102”

Configuration Registers (cont) Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Binary 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 The characters “0x” indicates that the following digits are in hexadecimal. Note that with reference to the config register, each hex character translates as a separate “nibble”, or a 4-bit, binary number. This is why the hex 0x2102 translates as the “Binary” line above

Configuration Registers (cont) The lowest four bits of the configuration register (bits 3, 2, 1, and 0) form the boot field. The order in which the switch/router looks for system bootstrap information depends on the boot field setting in the configuration register. When the boot field is set to either 0 or 1 (0-0-0-0 or 0-0-0-1), the system ignores any boot instructions in the system configuration file and the following occurs: When the boot field is set to 1 you will boot from an IOS image stored in ROM. When the boot field is set to 0, you must boot the operating system manually by giving a boot command to the system bootstrap program, or ROM monitor (ROMmon mode).

Configuration Registers (full text) 9

Checking the Register Value Router#sh version Cisco Internetwork Operating System Software IOS ™ C2600 Software (C2600-I-M), Version 12.0(3)T3 RELEASE SOFTWARE (fc1) [output cut] Configuration register is 0x2102

Configuration Meanings

Boot Field Meanings (Config Register bits 00 – 03)

Changing the Configuration Register Why would you want to change the config register? Several reasons: to force the system into the ROM monitor mode to select a boot source & default boot filename to enable or disable the Break function to set the console terminal baud rate to load operating software from ROM to enable booting from a TFTP server

Changing the Configuration Register One way to change the config register is to use the command below: Router(config)#config-register 0x0101 Router(config)#^Z Router#sh ver Configuration register is 0x2102 (will be 0x0101 at next reload) The command displays both the current value of the config register as well as the value at the next reload.

Recovering Passwords 1: Boot the router 1(a): interrupt the boot sequence by performing a break 2: Change the configuration register to turn on bit 6 (0x2142) 3: Reload the router 4: Enter the privileged mode 5: Copy the startup-config to running-config 6: Change the password 7: Reset the configuration register to the default value 8: Reload the router Note: You need physical access to the router to do this.

Recovering Passwords – (Step by step) 1: Boot the router & interrupt the boot sequence by performing a break using the Ctrl+Break key combination. You may need to upgrade your version of hyper-terminal in order for this to work successfully. (I’ve never had to do this, and I’ve used some pretty old versions of HyperTerminal; grain of salt here).

Recovering Passwords 2: Change the configuration register to turn on bit 6 (0x2142) rommon>confreg 0x2142 You must reset or power cycle for new config to take effect 3: Reload the router Type reset The router will reload & ask if you want to enter setup mode Answer NO 4: Enter the privileged mode Router>enable Router#

Recovering Passwords 5: Copy the startup-config to running-config Router#copy startup-config running-config 6: Change the password Router#config t Router(config)#enable secret cisco 7: Reset the configuration register to the default value Router(config)#config-register 0x2102 8: Reload the router

Backing up & Restoring the Cisco IOS Before you upgrade….. Copy the existing IOS to a TFTP host! Verify Flash Memory Router#sh flash System flash directory: File Length Name/status 1 8121000 c2500-js-1.112-18.bin [8121064 bytes used, 8656152 available, 16777216 total] 16384K bytes of processor board System flash (Read ONLY) Router#

Restoring or Upgrading the Cisco IOS #1: Ensure you have good connectivity to the TFTP host Router#ping 192.168.0.120 #2: Copy the IOS from the TFTP host to flash Router#copy tftp flash This copies the new IOS, currently in the default directory of the TFTP server, to NVRAM where it will become the operating system for the router, switch or other Cisco device being upgraded. The TFTP host must have a default directory specified Copying the IOS from a TFTP host to flash requires a router reboot 20 / 265

Backing up the Cisco IOS #1: Ensure you have good connectivity to the TFPT host Router#ping 192.168.0.120 #2: Copy the IOS from flash to the TFTP host Router#copy flash tftp This command copies the contents of flash (the old IOS version) to the TFTP host. The TFTP host must have a default directory specified

Backing up the Configuration 1: Verify the Current Configuration Router#sh run 2: Verify the Stored Configuration Router#sh start Verify available memory 3: Copy running-config to NVRAM Router#copy run start The configuration you are currently running becomes the config that you will now boot to, after copying it to NVRAM, the startup config. 4: Copy running-config to a TFTP host Router#copy run tftp A second backup

Restoring the Configuration Used when… You need to copy the startup-config to the running-config Errors made in editing the running-config Changes made at the TFTP host need to be copied to the running-config or startup-config Router#copy tftp run or Router#copy tftp start NOTE: The configuration file is ASCII. Any text editor will enable changes Erasing the Configuration Router#erase startup-config Note: When the router reboots it will be in setup mode See Supp Power Point 2 for recovering the Configuration using Xmodem: “Download using Xmodem from rommon >”

Table 1 Network Prefixes for Cisco IFS URLs Cisco IOS File System Cisco has a file system called IFS that allows you to work with files and directories just as you would from a DOS prompt. Some IFS commands use URLs as part of the command syntax. This link is to “Cisco IOS File System Command Syntax” http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfrintro.html#wp1071821 Below are some tables showing examples of the IFS: Table 1 Network Prefixes for Cisco IFS URLs Prefix Description ftp: Specifies a File Transfer Protocol (FTP) network server. rcp: Specifies an remote copy protocol (rcp) network server. tftp: Specifies a TFTP server.

Table 2 File ID Suffixes for Cisco IFS URLs Cisco IOS File System Table 2 File ID Suffixes for Cisco IFS URLs Prefix Suffix Options ftp: [[//[username[:password]@]location]/directory]/filename For example: ftp://network-config (prefix://filename) ftp://jeanluc:secret@enterprise.cisco.com/ship-config rcp: rcp:[[//[username@]location]/directory]/filename tftp: tftp:[[//location]/directory]/filename

Cisco IOS File System Prefix Description Table 3: File System Prefixes for Cisco IFS URLs  Prefix Description bootflash: Bootflash memory. disk0: Rotating disk media. flash: [partition-#] Flash memory. This prefix is available on all platforms flh: Flash load helper log files. null: Null destination for copies. Copy a remote file to null to find its size. nvram: NVRAM. This is the default location for the running-configuration file. slavebootflash: Internal Flash on slave RSP card of a router configured with 2 RSPs. slavenvram: NVRAM on a slave RSP card. slaveslot0: First PCMCIA card on a slave RSP card. slaveslot1: Second PCMCIA card on a slave RSP card. slot0: First PCMCIA Flash memory card. slot1: Second PCMCIA Flash memory card. xmodem: Obtain the file from a network machine using the Xmodem protocol. ymodem: Obtain the file from a network machine using the Ymodem protocol.

Cisco IOS File System The limitations of the IFS are, of course, that it is simply a tool to carry out some fairly basic tasks: copying files, transferring files, working with specific types of memory found in routers and switches, etc. But within these parameters, it does have some benefits: One of the benefits is that the file system’s user interface is universal — it’s not platform specific. You get to use the same syntax for all your commands on all of your routers. Another benefit is that it cuts down on all those obligatory prompts for a lot of the commands. If you want to enter a command, all you have to do is type all the necessary info straight into the command line. if you want to copy a file to an FTP server, all you do is: first indicate where the desired source file is on your router pinpoint where the destination file is on the FTP server determine the username and password you’re going to use, and type it all in on one line!

Using Cisco Discovery Protocol (CDP) A Cisco proprietary protocol Designed to collect information about directly attached & remote devices Hardware information Protocol information Useful in troubleshooting & documenting the network

Getting CDP Timers & Holdtime Information Configuration: CDP Timer: How often CDP packets are transmitted to all active interfaces CDP Holdtime: The amount of time that the device will hold packets received from neighbor devices Router#sh cdp Global CDP information Sending CDP packets every 60 seconds Sending a value of 180 seconds Router#config t Router(config)#cdp timer 90 Router(config)#cdp holdtime 240

Getting Neighbor Information Shows information about directly connected devices CDP packets are not passed through a Cisco switch Can only see what is directly attached Router#sh cdp nei (“nei” stands for “Neighbor”, i.e., “directly attached” devices). or Router#sh cdp neighbor detail Detailed information; hostname, IP address, etc

Getting Interface Traffic & Port Information Interface Traffic Information: CDP packets sent & received Errors with CDP Router# sh cdp traffic Port & Interface Information: Encapsulation on the line Timer & Holdtime for each interface Router# sh cdp interface

Using Telnet A virtual terminal protocol Part of the TCP/IP suite Allows connections to remote devices Gather information Run programs Note: The VTY passwords must be set on the routers in order for them to allow a telnet session.

Using Telnet Setting VTY passwords: RouterB#config t - to global config mode RouterB(config)#line vty 0 4 - to get to line-config mode, for telnet RouterB(config)#login - sets the state to enter login PW RouterB(config)#password cisco - set the login PW as “cisco” RouterB(config)#^Z - brings you back to privileged mode RouterA#172.16.10.2 - entering just an IP addr tries telnet Trying 172.16.10.2 … Open User Access Verification Password: RouterB>

Using Telnet Setting VTY password: Remember…. RouteBr#config t RouterB(config)#line vty 0 4 RouterB(config)#login RouterB(config)#password cisco RouterB(config)#^Z RouterA#172.16.10.2 Trying 172.16.10.2 … Open User Access Verification Password: RouterB> Remember…. VTY password is the user mode (>) password - not the enable mode (#) password With no enable/enable secret password set, the following happens: RouterB>en % No password set RouterB> This equates to good security! (in other words, with telnet, you MUST have a password set in order to access the utility!)

Telnet Commands Telnetting into Multiple Devices Ctrl+Shift+6 (release) X Checking Telnet Connections Router#sh sessions Checking Telnet Users Router#sh users Closing Telnet Sessions RouterB>exit RouterB>disconnect

Resolving Hostnames To use a hostname rather than an IP address to connect to a remote host a device must be able to translate the hostname to an IP address Build a host table on each router Build a Domain Name System (DNS) server

Building a Host Table Provides name resolution only on the router on which it is built [ip host name tcp_port_number ip_address]u Router(config)#ip host RouterB 172.16.10.2 Router(config)#ip host switch 192.168.0.148 Router#sh hosts Default TCP port number: 23 Router#RouterB RouterB#(Ctrl+Shift+6) (X) Router#switch

Using DNS to Resolve Names Used when you have many devices on your network Making DNS work… ip domain-lookup Turned on by default ip name-server Sets the IP address of the DNS server (up to 6 each) ip domain-name Appends the domain name to the hostname Ex: RouterA.neversail.navy.mil

Checking Network Connectivity Ping Displays the minimum, average, & maximum times it takes for a ping packet to find a specified system + return Router#ping RouterB Trace Shows the path a packet takes to get to a remote device Router#trace RouterB

Summary Go through all the written and review questions Go through the answers with the class 40