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List compiled by Alex Ward – 20/03/13
Command(s) |
Description |
| Router>ping | Basic ICMP ping function from within EXEC mode. |
| Router#ping {ip address} | A more detailed ICMP ping from within Privileged EXEX mode. |
| Router#traceroute {ip address} | Performs a traceroute for a given IP address |
| Router#configure terminal | Enters the Global Configuration Mode for higher level configuration |
| Router(config)#hostname RouterName | Sets the hostname of the router |
| Router(config)#ip route network-address subnet-mask {next-hop IP or exit-interface} | Adds a static route the routing table. (Remember to add in pairs to communicating router pair) |
| Router#copy running-config startup-config | Copies the current configuration into the register, for retrieval upon boot |
| Router(config)#line console 0
Router(config-line)#logging synchronous
|
Overcomes line interruption from router prompts, whilst typing commands. |
| CNTRL+SHIFT+6 | Exit process |
Security Configuration |
|
| Router(config-line)#exec-timeout {minutes} [seconds] | Controls the amount of time a console or virtual session can be idle before termination. Set to 00 for infinite, use only for labs! |
| Router(config)# banner login & message & | Create a login message. End this with a delimiting character like ‘#’ or ‘&’ |
| Router(config)#banner motd & message | Create a banner message. End with an ‘&’ |
| Router(config)#no ip domain-lookup | Prevents DNS look-up for lab setups |
| Router(config)#no enable password | Removes the enable password, often used in favour of enable secret password. |
| Router(config)#enable secret {password} | Provides better security by encrypting an enable password. It is separate to the line password! |
| Router(config)#line console 0
Router(config-line)#password cisco Router(config-line)#login Router(config-line)#exit |
Configures the console password. |
| Router(config)#line vty 0 4
Router(config-line)#password cisco Router(config-line)#login Router(config-line)#exit |
Configures the password for virtual terminal lines |
Interface Configuration |
|
| Router#show interfaces {interface name} | Displays details and the bandwidth of individual interfaces. |
| Router#show controllers [interface name] | Displays hardware details of an interface. Useful for fault finding serial connections. |
| Router#show ip interface brief | Shows a condensed brief of link state and IP addresses of attached interfaces & loopback(s) |
| Router(config)#interface [range] {interface ID} | Enters the interface configuration mode for a given interface or range of interfaces. |
| Router(config-if)#ip address {int ip address} {subnet mask} | Configure the ip address for a particular interface. |
Router-on-a-stick |
|
| Router(config)#interface {interface-ID.xxxx}
|
Configures a logical sub-interface on a physical interface. interfaceID.xxxx might be “fa0/1.10” for FastEthernet 0/1 sub-interface#10. |
| Router(config-subif)#encapsulation {type} {vlan-ID}
|
This is used in ‘router-on-a-stick’ configurations. After configuring a sub-interface as shown above, you must specify the encapsulation method, such as dot1q or isl etc… Then specify the VLAN to which this sub-interface should interact with. |
| Router(config-subif)#ip address {int ip address} {subnet mask} | Configure the ip address for a particular sub-interface. |
WAN Link Technologies |
|
| Router(config-if)#encapsulation {type} | Set the interface to use a specified protocol of encapsulation e.g. hdlc, ppp, frame-relay etc… |
Point-to-Point Protocol |
|
| Router#debug ppp [packet | negotiation | error | authentication | compression | cbcp] | Troubleshoot PPP, or use the options to troubleshoot PPP sub-processes. |
| Router(config-if)#encapsulation ppp | Set the interface to use PPP encapsulation method. |
| Router(config-if)#compress [predictor | stac] | Configure the router to use traffic compression. Optional elements enable the use of different algorithms. Only use with appropriate forms of traffic i.e. uncompressed. |
| Router(config-if)#ppp quality {%} | Apply Link Quality Monitoring. Specify the LCP percentage threshold for the link to become active. |
| Router(config-if)#ppp multilink | Enable load balancing across multiple physical links. |
| Router(config-if)#ppp authentication {chap | chap pap | pap chap | pap} [if-needed] [list-name | default ] [callin] | Configuration parameters for PPP authentication. CHAP PAP performs CHAP before PAP.
[if-needed] should not be applied alongside of PAP or CHAP – used with TACACS or XTACACS (only compatible with asynchronous interfaces). The list-name and default are only required for AAA/TACACS+. [callin] option is used to specify authentication on incoming calls only. |
| Router(config)#username {user} password {cisco} | Sets a local username and password for use with PPP authentication protocols. |
| Router(config)#ppp pap sent-username {user} password {password} | Set a PAP username and password for use with PPP coms leaving the local router. |
| Router(config-if)#aaa authentication ppp | Used to create a list for Authentication Authorization and Accounting in AAA/TACACS+ systems. |
Dynamic Routing |
|
| Router(config-if)#bandwidth [value] | Set the metric bandwidth of a link in kbps. This value is used to calculate the cost of a route in some dynamic protocols. Note: This does not alter the actual level 1 bandwidth. |
| Router#debug ip routing | Used to show modifications being made to the routing table in real-time. |
| Router#show ip protocols | Use to verify the dynamic routing protocol in use. |
| Router(config)#router ? | Show which versions of dynamic routing protocol the IOS version will support |
| Router(config-router)#no auto-summary | Prevents auto summarization occurring at major network boundaries. |
| Router(config-router)#default-information originate | Configure router to share static route information along with dynamic updates. |
RIPv1 & v2 |
|
| Router(config)#router rip | Enter RIP configuration state |
| Router(config-router)#passive-interface interface name | To prevent RIP updates being sent from a specific interface |
| Router#debug ip rip | Show RIP updates as they are sent and received |
| Router(config)#router rip
Router(config-router)#network address of directly connected classful network |
Configure RIPv1 advertisements on a specific interface. |
| Router(config-router)#default-information originate | Configure router to share static route information along with dynamic updates. |
RIPv2 |
|
| Router(config)#router rip
Router(config-router)#version 2 |
Enter RIP configuration state & configure RIPv2. |
EIGRP |
|
| Router(config)#router eigrp [A.S. number]
|
Enables EIGRP functionality on the router and allows for further configuration. |
| Router(config-router)#network network address
|
Advertise the specified network address to others |
| Router#show ip eigrp topology
Router#show ip eigrp topology [network address] |
Displays the EIGRP topology table on a specified router.
Including a [network address] Shows more detailed topology for a specific network. |
| Router(config-if)#ip summary-address eigrp [a.s.] [network] [mask] | Apply manual network summarization to a specific interface, to be shared with other EIGRP neighbours. |
| Router(config)#router eigrp [a.s.]
Router(config-router)#redistribute static |
This command will share the static route of the current router, with other EIGRP neighbours. |
OSPF |
|
| Router(config)#router ospf [process-ID] | Enables OSPF dynamic routing protocol, and enters configuration mode. Default process ID is 1. |
| Router(config-router)#network [network address] [wildcard mask] area [area ID] | Configures a network to be advertised by OSPF. Use 0 area ID for labs. This must be identical to all included OSPF routers in the same area. |
| Router#show ip ospf | Display detailed OSPF information. Such as process and router ID |
| Router#show ip ospf interface | Displays detailed information about OSPF interfaces |
| Router#show ip ospf neighbor | Show a brief list of OSPF neighbors and which interface they are connected to on the local router. |
| Router(config)#interface [OSPF interface]
Router(config-if)#ip ospf message-digest-key [key #] md5 [key value] Router(config-if)#exit Router(config)#router ospf [process ID] Router(config-router)#area [area ID] authentication message-digest |
Configures an interface for use with MD5 routing update authentication. Note: The same key must be used for an entire area! |
| Router(config-router)#router-id [network address] | Manually sets the router ID for the local router. (Will require a reload if neigbours are present). |
| Router#clear ip ospf process | This will erase and restart the current OSPF process. |
| Router(config-if)#ip ospf cost [calculated value] | Manually set the cost of a link. The value is calculated by 108 ÷ bandwidth of link in bps |
| Router(config-router)#auto-cost reference-bandwidth [value] | This can be used to simulate different connection speeds between routers. This must be set the same for the whole area. 10GigEthernet is 10000. |
| Router(config-if)#ip ospf hello-interval [seconds] | Change the hello interval from the default value: (multi-access is 10 seconds, or 30 seconds for NBMA segments). |
| Router(config-if)#ip ospf dead-interval [seconds] | Change the dead interval from the default value: (40 seconds). |
| Router(config-if)#ip ospf priority [int value] | Change the priority of an OSPF interface. This can alter eligibility for DR & BDR election. Range from 0-255, with Zero as lowest. Setting Zero will stop the router from participating in DR / BDR elections. |
Lesser Used Commands |
|
| Router#debug {process-name] | Debug a specific process. Such as ip routing – Show IP routes being learned instantaneously (Use sparingly) |
| Router#undebug all | Stop ALL debugging |
| Router#undebug {process-name} | Stop a debug of a specific process. |
| Router(config-if)#description R1 LAN | Provides a description of the interface |
| Router#reload | Reloads IOS from the NVRAM |
| Router(config)#no cdp run | Disables the CDP functionality that is enabled as standard. This improves security if not required. |
| Router(config-if)#no cdp enable | This disables CDP advertisements ONLY on the selected interface. |
| Router#show version | Provides a description of the version of IOS loaded and the memory register in use |
| Router#copy running-config tftp: | Backup Configuration Settings TO a TFTP Server |
| Router#copy tftp: running-config
Address or name of remote host []? xxx.xxx.xxx.xxx Source filename []? backup_cfg_for_my_router |
Copy configuration FROM a TFTP Server
|
Register Configuration |
|
| Router(config)#config-register [registerValue] | Set the configuration register to a value. Standard is usually set to: 0×2102.
Set to 0×2142 to disable the router from saving configurations. |
IOS v.11 Irregularities |
|
| Router(config)#subnet-zero
Router(config)#ip classless
|
This is a fix to the problem encountered when attempting to use a classless mask such as /30 with IOS v.11. |
If you have additional commands to add, please comment them below and I will update the list, thank you.
What the one to erase all configuration? Cheers
The procedure is slightly different on a router to a switch. For a router, if you don’t know the passwords on the router. Refer to the page “How to restore default IOS settings” under learning materials for CCNA.
If you do have access to the privileged EXEC mode on the router, use the config-register command above and set it to 0×2142.
After this, issue a reload command.
Once rebooted, the default settings are restored but if you want to be able to save a configuration you will have to set the register back to 0×2102 using the config-register command.
I hope that solves your problem.
CCNA/ICND1/ICND2 EXAMS WILL BE CHANGED EFFECTIVE AS OF 30 SEPTEMBER 2013. I say take your exams now before its too late, you will be forced to study more hard stuff than is current…all commands on this page will need updating to keep inline with the new exams.
Thanks for the advice BIGMAN. I will be taking the CCNA 640-802 composite exam shortly. For those who are interested take a look at the latest examination info here.