CCNA 5.9 Checking Network Connectivity & Troubleshooting

• Ping and traceroute command can be used to test connectivity to remote device (user & privileged mode)
• Ping command displays the min, avg & max times for a ping packet to reach a specific remote device and return
• Traceroute command shows the path a packet takes to reach a remote device
• Debug command is used to display router operation, traffic and error message (privileged mode)
• Show processes command show router's CPU utilization info

CCNA 5.8 Resolving Hostnames

• In order to use hostname to connect to a remote device, local device must be able to resolve hostname to IP addresses
• Host table on each router & DNS server can be used to resolve hostname

CCNA 5.7 Using Telnet

• In order to use telnet, VTY passwords has to be set on remote router
• Pressing Ctrl+Shift+6 key , then X key allows user to telnet into multiple devices simultaneously
• Show sessions command allows user to observe telnet connection made from user's router to a remote device
• Show users command allows user to list all active console and VTY ports in use on user's router
• Exit / disconnect command allows user to end a Telnet session

CCNA 5.6 Cisco Discovery Protocol (CDP)

• CDP is a proprietary protocol designed to help administrators collect information about both locally attached and remote devices
• Show cdp command gives user info on CDP timer & holdtime
• CDP timer is how often CDP packets are transmitted out all active interfaces
• CDP holdtime is the amount of time that the device will hold packets received from neighbor devices
• show cdp neighbors command deliver info (device ID, local interface, holdtime, capability, platform & port ID) about locally connected devices
• show cdp neighbors detail command deliver extra info on IP address & IOS version
• show cdp traffic command displays info about interface traffic (amount of CDP packets sent & received)
• show cdp interface command display info about CDP status on router interfaces or switch ports

CCNA 5.5 Backing Up and Restoring Cisco Configuration

• Cisco router configuration can be back up & restored through TFTP, Cisco IFS & SDM
• Changes on router configuration are stored in running-config file
• Router config changes will be lost when router is reboot or powered down (if it is not copy to startup-config)
• Copy running-config tftp command is used to copy router's configuration from a router to TFTP server
• Copy tftp running-config command is used to restore router's configuration from a TFTP server to a router

CCNA 5.4 Backing up and restoring Cisco IOS

• Cisco IOS can be back up & restored through TFTP, Cisco IFS & SDM
• Before upgrading IOS, user have to verify router flash memory space through show flash or show version command
• Copy flash tftp command is used to backup Cisco IOS to a TFTP server
• Copy tftp flash command is used to restore or upgrade Cisco IOS from a TFTP server
• Cisco IOS File System (IFS) allows user to work with files and directories through Windows DOS prompt

CCNA 5.3 Managing Configuration Register

• All Cisco routers have a 16-bit software register (Configuration) in NVRAM
• Configuration register loads IOS from flash memory and startup-config file from NVRAM
• Default configuration setting on Cisco router is 0x2102

• 0x means that the digits that follow are in hexadecimal
• Software configuration meaning:

• Boot Field:

• Show version command can be used to check current value of configuration register
• Configuration register value can be changed to modify how the router boots and runs
• Config-register command can be used to change config register value
• To recover a router password, user have to turn on bit 6 (0x2142) of configuration register to ignore the NVRAM contents (start-up config)
• Ctrl +Break key is used to interrupt boot sequence and enter ROM monitor mode
• I command is used to reset the router
• boot system command allows user to tell router which file to boot from flash memory
• Cisco's suggested IOS backup routine: flash, TFTP host, ROM

CCNA 5.2 Router Boot Sequence

1. Perform POST to test hardware components' functionality (stored in ROM)
2. Bootstrap loads IOS from flash memory
3. IOS searches for valid config file (startup-config) in NVRAM
4. Router copies startup-config file from NVRAM to RAM and named it running-config file

CCNA 5.1 Internal Components of Cisco Router

• Cisco Router Components:

CCNA 4.6 Cisco Security Device Manager (SDM)

• Cisco's SDM allows user to configure a router from an HTTP or HTTPS interface

CCNA 4.5 View, Save & Erase Config

• To manually save the config file from DRAM to NVRAM, use copy running-config start-up config command
• To view config file, use show running-config (sh run) / startup-config (sh start) command
• To delete startup-config file, use erase startup-config command

CCNA 4.4 Router Interfaces

• Different Cisco routers have different interface methods
• Interface commands example:

interface e0 (2500)

interface fastethernet 0/0 (2600)

interface serial 0/1/0 (2800)

• No shutdown interface command enables an interface
• Users can check an interfaces' status via show interface or show running-config commands
• To configure IP addresses on an interface, use the ip address command from interface configuration mode
• | (output modifier) command allows user to goto specific ouput within the configurations
• To configure a serial interface, user can use clock rate command to set the clock rate of DCE connection (for DTE with no CSU/DSU)
• show controllers int command allows user to check whether a router has DCE cable connected to it
• Bandwidth command allows user to set data rate on serial link (for EIGRP, OSPF best path calculation)

CCNA 4.3 Cisco Router & Switch Admin Configs

• Config commands that helps user to admin the network are: hostname, banner, passwords & interface description (for network troubleshooting & maintenance)
• Hostname command allows user to set identity to the router
• Banner command allows user to show personal information/message on router
• Example of banner command includes: Exec, Incoming, Login & MOTD commands
• Five passwords are used to secure Cisco router: console, auxiliary, telnet (VTY), enable password & enable secret.
• Description command allows user to set descirption on a router interface
• do command allows user to view configurations and statistics from config mode