- 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
Thursday, July 30, 2009
CCNA 5.9 Checking Network Connectivity & Troubleshooting
Wednesday, July 29, 2009
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
Tuesday, July 28, 2009
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
Thursday, July 23, 2009
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
Wednesday, July 22, 2009
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
![](http://4.bp.blogspot.com/_GKROBw-pB0U/Smczj_tHyxI/AAAAAAAAAHU/IeWI3hOl-4U/s400/2009-07-22_084207.jpg)
- 0x means that the digits that follow are in hexadecimal
- Software configuration meaning:
![](http://3.bp.blogspot.com/_GKROBw-pB0U/Smc0mG6Z8mI/AAAAAAAAAHc/XD3S59b68Q4/s400/2009-07-22_084647.jpg)
- Boot Field:
![](http://4.bp.blogspot.com/_GKROBw-pB0U/Smc1iPVyPDI/AAAAAAAAAHk/pJ3zEu2o94I/s400/2009-07-22_085047.jpg)
- 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
Monday, July 20, 2009
CCNA 5.2 Router Boot Sequence
- Perform POST to test hardware components' functionality (stored in ROM)
- Bootstrap loads IOS from flash memory
- IOS searches for valid config file (startup-config) in NVRAM
- Router copies startup-config file from NVRAM to RAM and named it running-config file
Thursday, July 16, 2009
CCNA 4.6 Cisco Security Device Manager (SDM)
- Cisco's SDM allows user to configure a router from an HTTP or HTTPS interface
Monday, July 13, 2009
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
Thursday, July 2, 2009
CCNA 4.4 Router Interfaces
- Different Cisco routers have different interface methods
- Interface commands example:
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)
Wednesday, July 1, 2009
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
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