Router Startup and Config

CCNA Guide to Cisco Networking

Chapter 7: Router Startup and Configuration

CCNA Guide to Cisco Networking Fundamentals

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Objectives

• Understand router startup• Describe and use the Cisco Discovery

Protocol• Understand configuration management

commands for Cisco routers and the 1900 series switch

• Configure IP on the Cisco router and the 1900 series switch

• Troubleshoot router connectivity problems


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Router Startup

• Boot process steps

• Test hardware

• Load bootstrap program

• Locate and load the Cisco IOS

• Locate and load the router configuration file


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Router Startup (continued)


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• POST– Power-on self test (POST)

• Bootstrap program• Diagnostic test for hardware• ROM monitor

– Read-only memory (ROM)


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• Configuration register– 16-bit setting stored in NVRAM

• Hexadecimal code

– Configuration register controls 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

– “show version” command


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• ROM monitor mode– (>) or (rommon>)– ROM monitor mode initiates when

• Manually configured• Cannot locate Cisco IOS• A forced system break

– Ctrl+”break” keys with in 60 seconds (Hyperterm)– “config-register 0x2100” command

• “show version” command• “copy run start” command• “reload” command


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• RxBoot mode– Cannot boot from flash– Cannot locate IOS or corrupt IOS– RxBoot mode prompt

• Router hostname followed by (boot)• Router(boot)

– Limited set of IOS commands to configure the router


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• Cisco IOS– Usually loaded from flash memory– “show flash” command– “show version” command– Fallback options for loading the IOS

• Load from TFTP server• Cannot find IOS, load from ROM (basic IOS)

– Default fallback sequence to locate the IOSFlashTFTP serverROM


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Boot System Commands

• Alternative to the “config-register” command• Configure router to locate IOS• Boot system commands are stored in start-up

configuration file• Boot system commands only work when last

digit of config-register is “2”• Boot system command structure

– “boot system [location of IOS] [IOS file name]”– “boot system tftp c1700-j-mz.122-5(t).bin”


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Boot System Commands

• Router will broadcast looking for a tftp a computer running TFTP software

• TFTP server must be on a subnet directly connected to the router broadcasting for TFTP services

• Multiple “boot system” commands maybe entered for redundancy

• “copy run start” command


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Upgrading The IOS

• Upgrading IOS check list– Ensure router has enough memory

• “show flash” command

– Backup current IOS to a TFTP server• Identify the current IOS file name• “show flash” command• “show version” command

• “copy tftp flash” command


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Router Configuration Files

• Startup-config file– Also known as the backup configuration file

• Startup-config file is loaded into RAM at which point it becomes the running-config file

• “show startup-config” command• Reboot the system to revert to the settings is the

startup-config file– Power off and on– “reload” command


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Router Configuration Files (continued)

• “copy start run” or “copy tftp run” merges with the current running-config settings

• No “erase running-config” command

• “erase startup” command– Not the same as “erase nvram”


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Methods For Making Changes

• Changes can be implemented and tested without saving to the startup-config file

• Changes to the running configuration take place immediately

• Basic steps for implementing changes– Make desired changes– Examine the changes and the affects– Determine if the changes meet the desired results– Remove changes if they do not meet the desired

results or simply reboot the system– If desired result have been met then save to startup-

config file


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CDP

• Cisco discovery protocol (CDP)• Proprietary Data Link layer protocol• Shares basic system and configuration

settings to directly connected Cisco devices– Routers– Switches– Hubs– Access servers


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CDP (continued)

• “show cdp neighbors” command provides the following options– Ethernet

• Learn about Ethernet interfaces attached to neighbors– Null

• Learn about interfaces of a neighbor that does not have an address assigned

– Serial• Information about neighbors connected to serial interfaces

– Detail• Detailed information about the CDP neighbor and all

attached devices• This detailed information includes device identification,

remote interface type, and remote IP address


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CDP (continued)

• Low-overhead protocol

• Broadcasts information ever 60 seconds by default

• Enabled on all Cisco devices by default

• Possible to turn off CDP– Entire router– Individual interfaces


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IP On The Router

• IP maybe configured by the extended setup program

• Steps to manually configure IP on the router and the interface– Enter global configuration mode– “ip routing” command– Enter interface mode for desired interface– Assign IP address– Activate the interface

• “no shutdown” command


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IP On The Router (continued)

• Two ways to have multiple IPs on an interface– Secondary IP address– Subinterfaces

• “term ip netmask-format” command


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IP On The Switch

• IP address are not required on a switch

• Switches operate on the Data Link layer (MAC) addresses

• To remotely manage a switch assign– IP address for the entire switch– Assign a gateway for the switch

• By default switches are not configured with an IP address or a gateway


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IP Connectivity


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Telnet

• Connects at the highest layer of the OSI model

• Provides remote access

• Virtual terminal ports

• Successful telnet connection means connectivity at all layers


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IP Host Names

• Refer to a remote host or router by name

• Address to name mapping on the router

• “ip host router_central 192.168.10.1”

• “show hosts” command

• “ip host” command is local service

• DNS is a non-local name resolution service


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IP Host Names (continued)

• DNS is a non-local name resolution service

• “ip name-server 192.168.10.3”


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Ping And Trace

• Test Internetwork layer connectivity of the TCP/IP model

• Available in User EXEC and Privileged EXEC modes

• ICMP– Echo request– Echo reply

• “ping” command and extended mode ping• “traceroute” command


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Ping And Trace (continued)

• Ping utility send five packets and will have the following replies– !: Successful receipt of the ICMP echo– .: Request timed out– U: Destination was unreachable– C: Congestion experienced– I: Ping interrupted– ?: Packet type unknown– &: Packet TTL exceeded


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Ping And Trace (continued)

• Traceroute responses– !H: Indicates that a router received, but didn’t

forward, the ICMP echo request– P: Protocol unreachable– N: Network unreachable– U: Port unreachable– *: Request timed out


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IP Route

• If ping or traceroute fail check the routing table

• “show ip route” command– Displays the routing table– Routing table displays

• Directly connected networks• Dynamically learned networks• Statically assigned routes


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Checking The Interface

• If the interface is down then packets cannot be delivered

• “show interface” command– Check the status of the interface– View the interface configuration

• Possible interface states– Serial0/0 is up, line protocol is up– Serial0/0 is up, line protocol is down– Serial0/0 is down, line protocol is down– Serial0/0 is administratively down, line protocol is

down


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Checking The Interface (continued)

• Clear counters– Routers keep detail statistics (counters)– Sometimes beneficial to clear the existing counters– “clear interface serial 0/0”

• Debug– Debugs provides information on real-time router

events– Resource intensive

• Negative impact on router performance• Do not run for extended periods of time

• “no debug all”, “undebug all”


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Router Password Recovery

• Password recovery is not the same for all router and switch modules

• Cisco.com has instructions available for every Cisco network device

• Cannot perform password recovery through telnet or other remote means

• Password recovery example (2600 series router)– Connect to router via console connection


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Router Password Recovery (continued)

• Password recovery example (2600 series router) (continued)– Connect to router via console connection– Power cycle the router (cold boot)– Enter break sequence within 60 seconds of boot

• Hyperterm (Ctrl+break), Tera Term (ALT+b)

– At rommon> prompt type “confreg 0x2142”– Enter the “reset” command to reboot the router– Do not enter setup sequence– “copy start run” command


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Router Password Recovery (continued)

• Password recovery example (2600 series router) (continued)– Change passwords– “config-register 0x2102” command to reset

router– “copy run start” command


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Summary

• When the router boots, it follows a set routine• Although the router’s boot process can vary, the

typical boot process follows this sequence: – First, the router checks all of its internal hardware

components during a process called the POST (power-on self-test)

– Next, the router loads the basic configuration routine known as the bootstrap program

– Then, the bootstrap attempts to locate the Cisco IOS, which in turn loads the router configuration file


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Summary (continued)

• If the Cisco IOS is set to load from a TFTP server, but the TFTP server cannot be located, then the IOS will boot from flash memory

• If the IOS cannot be found in flash memory or on the TFTP server, then a limited version will boot from ROM

• If the Cisco IOS is set to load a configuration file from a TFTP server, but the file or server is not available, the configuration file will be loaded from NVRAM

• However, if a configuration file is not available in NVRAM or on a TFTP server, then the automated setup routine will be initialized


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Summary (continued)

• The Cisco Discovery Protocol (CDP) is proprietary to Cisco devices

• This protocol shares information between Cisco devices about other local Cisco devices

• CDP uses broadcasts to update neighbors every 60 seconds by default (the update time interval is configurable)

• Devices share information about their interface configurations and connections to other devices

• IP configuration on Cisco switches and routers is similar: the command syntax is ip address [IP address] [subnet mask]


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Summary (continued)

• When you configure an address for a router interface, you must be in interface configuration mode (config-if )

• When you configure an IP address for a Catalyst 1900 switch, you need only be in global configuration mode

• These switches don’t require IP addresses; you need only configure one if you intend to remotely manage the switch

• You can verify router connectivity to other systems by using telnet to determine if there is Application layer connectivity


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Summary (continued)

• If you cannot get connectivity at the Application layer, try trace and ping

• Then, check your routing table with the show ip route command to determine if there is a problem with the Network layer

• One of the most important troubleshooting commands is the show interfaces command

• If your interfaces are not up, you cannot route packets

Documents

Router Startup and Config