logging synchronous Command - Networking How-to

logging synchronous Command Router(config)#line con 0 Router(config-line)#logging synchronous Turns on synchronous logging. Information items sent to console will not interrupt the command you are typing. The command will be moved to a new line Tip: Ever try to type in a command and an informational line appears in the middle of what you were typing? Lose your place? Do not know where you are in the command, so you just press Enter and start all over? The logging synchronous command will tell the router that if any informational items get displayed on the screen, your prompt and command line should be moved to a new line, so as not to confuse you. The informational line does not get inserted into the middle of the command you are trying to type. If you were to continue typing, the command would execute properly, even though it looks wrong on the screen.

no ip domain-lookup Command

Router(config)#no ip domain-lookup Router(config)#	Turns off trying to automatically resolve an unrecognized command to a local host name

Tip:

Ever type in a command incorrectly and are left having to wait for a minute or two as the router tries to translate your command to a domain server of 255.255.255.255? The router is set by default to try to resolve any word that is not a command to a DNS server at address 255.255.255.255. If you are not going to set up DNS, turn this feature off to save you time as you type, especially if you are a poor typist.

Assigning a Local Host Name to an IP Address - Networking How-to

Assigning a Local Host Name to an IP Address

Router(config)#ip host london 172.16.1.3	Assigns a host name to the IP address. After this assignment, you can use the host name instead of an IP address when trying to Telnet or ping to that address
Router#ping london
=
Router#ping 172.16.1.3

Tip:

The default port number in the ip host command is 23, or Telnet. If you want to Telnet to a device, just enter the IP host name itself:

Router#london = Router#telnet london = Router#telnet 172.16.1.3 

Setting the Clock Time Zone on a Cisco Router - Networking How-to

Setting the Clock Time Zone

Router(config)#clock timezone EST 5	Sets the time zone for display purposes. Based on coordinated universal time (Eastern Standard Time is 5 hours behind UTC)

Creating an MOTD Banner on a Router - Networking How-to

Creating an MOTD Banner Router(config)#banner motd # This is a secure system. Authorized Personnel Only! # Router(config)# # is known as a delimiting character. The delimiting character must surround the banner message and can be any character so long as it is not a character used within the body of the message

Configuring an Ethernet/Fast Ethernet Interface on a Router - Networking How-to

Configuring an Ethernet/Fast Ethernet Interface

Router(config)#int fa0/0	Moves to Fast Ethernet 0/0 interface mode
Router(config-if)#description Accounting LAN	Optional descriptor of the link is locally significant
Router(config-if)#ip address 192.168.20.1 255.255.255.0	Assigns address and subnet mask to interface
Router(config-if)#no shut	Turns interface on

Configuring a Serial Interface on a Cisco Router - Networking How-to

Configuring a Serial Interface

Router(config)#int s0/0	Moves to interface Serial 0/0 mode
Router(config-if)#description Link to ISP	Optional descriptor of the link is locally significant
Router(config-if)#ip address 192.168.10.1 255.255.255.0	Assigns address and subnet mask to interface
Router(config-if)#clock rate 56000	Assigns a clock rate for the interface
Router(config-if)#no shut	Turns interface on

Tip:

The clock rate command is used only on a serial interface that has a DCE cable plugged into it. There must be a clock rate set on every serial link between routers. It does not matter which router has the DCE cable plugged into it, or which interface the cable is plugged into. Serial 0 on one router can be plugged into Serial 1 on another router.

Moving Between Router Interfaces - Networking How-to

Moving Between Interfaces

What happens in Column 1 is the same thing occurring in Column 2.

Router(config)#int s0	Router(config)#int s0	Moves to interface S0 mode
Router(config-if)#exit	Router(config-if)#int e0	In int S0, move to E0
Router(config)#int e0	Router(config-if)#	In E0 mode now
Router(config-if)#		Prompt does not change; be careful

Interface Names on a Cisco Router - Networking How-to

Interface Names

One of the biggest problems that new administrators face is the interface names on the different models of routers. With all of the different Cisco devices that are in production networks today, some administrators are becoming confused on the names of their interfaces.

The following chart is a sample of some of the different interface names for various routers. This is by no means a complete list. Refer to the hardware guide of the specific router that you are working on to see the different combinations, or use the following command to see which interfaces are installed on your particular router:

router#show ip interface brief 

Router Model	Port Location/Slot Number	Slot/Port Type	Slot Numbering Range	Example
2501	On Board	Ethernet	Interface-type Number	ethernet0 (e0)
	On Board	Serial	Interface-type Number	serial0 (s0) & s1
2514	On Board	Ethernet	Interface-type Number	e0 & e1
	On Board	Serial	Interface-type Number	s0 & s1
1721	On Board	FastEthernet	Interface-type Number	fastethernet0 (fa0)
	Slot 0	WAC (WIN Interface Card) (Serial)	Interface-type Number	s0 & s1
1760	On Board	Fast Ethernet	Interface-types 0/port	fa0/0
	Slot 0	WIC/VIC (Voice Interface Card)	Interface-type 0/port	s 0/0 & s0/1 v0/0 & v0/1
	Slot 1	WIC/VIC	Interface-type 1/port	s1/0 & s1/1 v1/0 & v1/1
	Slot 2	VIC	Interface-type 2/port	v2/0 & v2/1
	Slot 3	VIC	Interface-type 3/port	v3/0 & v3/1
2610	On Board	Ethernet	Interface-type 0/port	e0/0
	Slot 0	WIC (Serial)	Interface-type 0/port	s0/0 & s0/1
2611	On Board	Ethernet	Interface-type 0/port	e0/0 & e0/1
	Slot 0	WIC (Serial)	Interface-type 0/port	s0/0 & s0/1
2620	On Board	FastEthernet	Interface-type 0/port	fa0/0
	Slot 0	WIC (Serial)	Interface-type 0/port	s0/0 & s0/1
2621	On Board	FastEthernet	Interface-type 0/port	fa0/0 & fa 0/1
	Slot 0	WIC (Serial)	Interface-type 0/port	s0/0 & s0/1
1841	On Board	FastEthernet	Interface-type 0/port	fa 0/0 & fa 0/1
	Slot 0	High Speed WAN Interface Card (HWIC)/WIC/VWIC	Interface-type 0/slot/port	s0/0/0 & s0/0/1
1841	Slot 1	HWIC/WIC/VWIC	Interface-type 0/slot/port	s0/1/0 & s0/1/1
2801	On Board	FastEthernet	Interface-type 0/port	fa0/0 & fa 0/1
	Slot 0	VIC/VWIC (voice only)	Interface-type 0/slot/port	voice0/0/0 voice0/0/3
	Slot 1	HWIC/WIC/VWIC	Interface-type 0/slot/port	0/1/0 0/1/3 (single-wide HWIC) 0/1/0 0/1/7 (double-wide HWIC)
	Slot 2	WIC/VIC/VWIC	Interface-type 0/slot/port	0/2/0 - 0/2/3
	Slot 3	HWIC/WIC/VWIC	Interface-type 0/slot/port	0/3/0 0/3/3 (single-wide HWIC) 0/3/0 - 0/3/7 (double-wide HWIC)
2811	Built into Chassis Front	USB	Interface-type port	usb0 & usb 1
	Built into Chassis Rear	FastEthernet Gigabit Ethernet	Interface-type 0/port	fa0/0 & fa 0/1 gi0/0 & gi0/1
	Slot 0	HWIC/HWIC-D/WIC/VWIC/VIC	Interface-type 0/slot/port	s0/0/0 & s0/0/1 fa0/0/0 & 0/0/1
	Slot 1	HWIC/HWIC-D/WIC/VWIC/VIC	Interface-type 0/slot/port	s0/1/0 & s0/1/1 fa0/1/0 & 0/1/1
	NME Slot	NM/NME	Interface-type 1/port	gi1/0 & gi1/1 s1/0 & s1/1

Show Commands on Cisco Routers - Networking How-to

show Commands

Router#show ?	Lists all show commands available
Router#show interfaces	Displays statistics for all interfaces
Router#show interface serial 0	Displays statistics for a specific interface, in this case Serial 0
Router#show ip interface brief	Displays a summary of all interfaces, including status and IP address assigned
Router#show controllers serial 0	Displays statistics for interface hardware. Statistics display if the clock rate is set and if the cable is DCE, DTE, or not attached
Router#show clock	Displays time set on device
Router#show hosts	Displays local host-to-IP address cache. These are the names and addresses of hosts on the network to which you can connect
Router#show users	Displays all users connected to device
Router#show history	Displays history of commands used at this edit level
Router#show flash	Displays info about Flash memory
Router#show version	Displays info about loaded software version
Router#show arp	Displays the ARP table
Router#show protocols	Displays status of configured Layer 3 protocols
Router#show startup-config	Displays configuration saved in NVRAM
Router#show running-config	Displays configuration currently running in RAM

Password Encryption on a Router/Switch - Networking How-to

Password Encryption

Router(config)#service password-encryption	Applies a weak encryption to passwords
Router(config)#enable password cisco	Sets enable password to cisco
Router(config)#line con 0	...
Router(config-line)#password Cisco	Continue setting passwords as above
	...
Router(config)#no service password-encryption	Turns off password encryption

Caution:

If you have turned on service password encryption, used it, and then turned it off, any passwords that you have encrypted will stay encrypted. New passwords will remain unencrypted.

Configuring Passwords on a Cisco Router - Networking How-to

Configuring Passwords

Works on both routers and switches.

Router(config)#enable password cisco Sets enable password

Router(config)#enable secret class Sets enable secret password

Router(config)#line con 0 Enters console-line mode
Router(config-line)#password console Sets console-line mode password to console
Router(config-line)#login Enables password checking at login

Router(config)#line vty 0 4 Enters vty line mode for all five vty lines
Router(config-line)#password telnet Sets vty password to telnet
Router(config-line)#login Enables password checking at login

Router(config)#line aux 0 Enters auxiliary line mode
Router(config-line)#password backdoor Sets auxiliary line mode password to backdoor
Router(config-line)#login Enables password checking at login

Caution:

enable secret password is encrypted by default. enable password is not. For this reason, recommended practice is that you never use the enable password. Use only the enable secret password in a router configuration.

Caution:

You cannot set both enable secret and enable password to the same password. Doing so defeats the use of encryption.

Networking How-to: Configuring a Router Name

This command works on both routers and switches.

Router(config)#hostname Cisco	Name can be any word you choose
Cisco(config)#

Networking How-to: Cisco Router Modes

Router Modes

Router>	User mode
Router#	Privileged mode
Router(config)#	Global configuration mode
Router(config-if)#	Interface mode
Router(config-subif)#	Subinterface mode
Router(config-line)#	Line mode
Router(config-router)#	Router configuration mode

Tip:

There are other modes than these. Not all commands work in all modes. Be careful. If you type in a command that you know is correctshow run, for exampleand you get an error, make sure that you are in the correct mode.