CCNA2_M5_Managing_Cisco_IOS_Software (1130727)
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CCNA – Semester2Module 5Managing Cisco IOS SoftwareObjectives• Router boot sequence and verification• Identify the configuration register values• Save and restore configuration files• Save and restore IOS imagesRouter Boot Sequence andVerificationRouter Startup SequenceLocating the Cisco IOS SoftwareBoot IOS from Flash Memory• A system image from flash memory can be loaded. Theadvantage is that information stored in flash memory is notvulnerable to network failures.Boot IOS from TFTP• In case flash memory becomes corrupted, a systemimage can be loaded from a TFTP server.Boot IOS from ROM• If flash memory is corrupted and the network serverfails to load the image, booting from ROM (ifavailable) is the final bootstrap option in software.Configuration register• The order in which the router looks for systembootstrap information depends on the boot fieldsetting in the configuration register.• The configuration register is a 16-bit register inNVRAM.Configuration register• Use a hexadecimal number to expressconfiguration register value .16-bit register0x0 0 0 0Bit: 16••••••0 – 3:6:8:11-12:13:15:0 0 0 00 0 0 06Boot fieldIgnore NVRAM contentsBreak disabledConsole line speedBoot ROM if network boot failsDiagnostic and ignore NVRAM0 0 0 03 2 1 0Configuration register: Boot field (2)• Router(config)# config-register 0x2102• Router(config)# exit• Router# show versionshow versionCisco Internetwork Operating System SoftwareIOS (tm) 2500 Software (C2500-D-L), Version 12.0(10), RELEASE SOFTWARE (fc1)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Mon 20-Mar-00 22:33 by phanguyeImage text-base: 0x0303882C, data-base: 0x00001000ROM: System Bootstrap, Version 11.0(10c), SOFTWAREBOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASESOFTWARE (fc1)SGCTT-HCM uptime is 1 week, 1 day, 1 hour, 9 minutesSystem restarted by power-onSystem image file is "flash:c2500-d-l.120-10"cisco 2500 (68030) processor (revision N) with 2048K/2048K bytes of memory.Processor board ID 23101339, with hardware revision 00000000Bridging software.X.25 software, Version 3.0.0.1 Ethernet/IEEE 802.3 interface(s)2 Serial network interface(s)32K bytes of non-volatile configuration memory.8192K bytes of processor board System flash (Read ONLY)Configuration register is 0x2102The router boot processROM monitorinitializes0Stays in ROMmonitorBoots the image1What isBootin boot ROMfield?or boot flash2 to FyesnoBootcommandsin NVRAM ?Executes bootRouter’scommandsFallback sequencePassword RecoveryStartCold Boot routerCtrl + BreakWithin 60sIn 25xx routersIn 26xx routerso/r 0x2142confreg 0x2142iPassword RecoveryInitialConfig?NenableCopy start runConf termEnable secret ciscoPassword RecoveryConfig-register 0x2102Ctrl-ZCopy Run StartTroubleshooting IOS boot failure• In the event that the router does not boot properly,there are several things that could be wrong:––––Configuration file has missing or incorrect boot system statementIncorrect configuration register valueCorrupted flash imageHardware failureIncorrect Boot System Statement• Use the show running-config command and lookfor a boot system statement near the top of theconfiguration.• If the boot system statement points to anincorrect IOS image, delete the statement usingthe “no” version of the command.Incorrect configuration register value• An incorrect configuration register setting willprevent the IOS from loading from flash.• The value in the configuration register tells therouter where to get the IOS.• This can be confirmed by using the show versioncommandCorrupted flash image• If this is the case, an error message should be displayedduring boot.
That message may take one of several forms.Some examples are:––––open: read error...requested 0x4 bytes, got 0x0trouble reading device magic numberboot: cannot open "flash:"boot: cannot determine first file name on device "flash:"ú• If the flash image is corrupt, a new IOS should be uploadedinto the router.Hardware failure• If none of the above appears to be the problem,the router could have a hardware failure.• If this is the case, the Cisco TechnicalAssistance (TAC) center should be contacted.• Although hardware failures are rare, they dooccur.Managing the Cisco File SystemSoftware Components in Memory• Routers and switchesdepend on software fortheir operation.
The twotypes of softwarerequired are operatingsystems andconfiguration files.Cisco IOS File System• Beginning with version 12 of the IOS, a single interfaceto all the file systems that a router uses is provided. Thisis referred to as the Cisco IOS File System (IFS).• The IFS provides a single method to perform all the filesystem management that a router uses.• This would include the flash memory file systems, thenetwork file systems (TFTP, rcp, and FTP), and readingor writing data (such as NVRAM, the runningconfiguration, ROM).IOS Version 12.x commands••IOS naming conventionsThe IFS uses the URLconvention to specifyfiles on networkdevices and thenetwork.The URL conventionidentifies the locationof the configurationfiles following thecolon as[[[//location]/directory]/filename]Managing configuration files using TFTPManaging configuration files using copy andpaste• Another way to create a backup copy of theconfiguration is to capture the output of theshow running-config command• Input configuration file using eather HyperTerminal-Send Text or Windows Buffer (Copyand Paste)Managing IOS images using TFTPEnvironment variables• The environmental variables provide a minimalconfiguration to allow for the TFTP of the IOS.• The ROMmon TFTP transfer works only on thefirst LAN port so a simple set of IP parametersare set for this interface.Setting environment variables• Start router and press Ctrl+Break• Configure the environment variables–––––––––IP_ADDRESS= {ip_address}IP_SUBNET_MASK={ip_subnet_mask}DEFAULT_GATEWAY={default_gateway}TFTP_SERVER={tftpserver_ip_address}TFTP_FILE={IOS_filename}setsync (save environment variables in NVRAM)tftpdnldreset (after download completed)Summary••••Identifying stages of the router boot sequenceUsing the boot system commandIdentifying the configuration register settingsManaging configuration files using copy-andpaste• Managing system files with TFTPCCNA2 – Module5.
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