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10 Commands You Need to Know When Using the Cisco IOS

August 6 2012 , Written by Cisco & Cisco Router, Network Switch Published on #Cisco & Cisco Network

Preface: Becoming proficient with the Cisco IOS means learning some essential commands. This quick reference describes 10 commands you’ll need to rely on when handling various configuration and troubleshooting tasks.

The Cisco IOS provides thousands of commands, and configuring it can be challenging. Here are 10 commands you need to know, inside and out, when using the Cisco IOS.Cisco-IOS-Commands.JPG

#1: The “?”

It may seem entirely too obvious that you should know how to type ? to ask for help when using the Cisco IOS. However, the Cisco IOS is completely different from other operating systems when it comes to using the question mark (help key). As the IOS is a command-line operating system with thousands of possible commands and parameters, using the ? can save your day.

 

You can use the command in many ways. First, use it when you don’t know what command to type. For example, type ? at the command line for a list of all possible commands. You can also use ? when you don’t know what a command’s next parameter should be. For example, you might typeshow ip ? If the router requires no other parameters for the command, the router will offer CR as the only option. Finally, use ? to see all commands that start with a particular letter. For example,show c? will return a list of commands that start with the letter c.

 

#2: show running-configuration

The show running-config command shows the router, switch, or firewall’s current configuration. The running-configuration is the config that is in the router’s memory. You change this config when you make changes to the router. Keep in mind that config is not saved until you do a copy running-configuration startup-configuration. This command can be abbreviated sh run.

 

#3: copy running-configuration startup-configuration

This command will save the configuration that is currently being modified (in RAM), also known as the running-configuration, to the nonvolatile RAM (NVRAM). If the power is lost, the NVRAM will preserve this configuration. In other words, if you edit the router’s configuration, don’t use this command and reboot the router–those changes will be lost. This command can be abbreviatedcopy run start. The copy command can also be used to copy the running or startup configuration from the router to a TFTP server in case something happens to the router.

 

#4: show interface

The show interface command displays the status of the router’s interfaces. Among other things, this output provides the following:

  • Interface status (up/down)
  • Protocol status on the interface
  • Utilization
  • Errors
  • MTU

This command is essential for troubleshooting a router or switch. It can also be used by specifying a certain interface, like shint fa0/0.

 

#5: show ip interface

Even more popular than show interface are show ip interface and show ip interface brief. Theshow ip interface command provides tons of useful information about the configuration and status of the IP protocol and its services, on all interfaces. The show ip interface brief command provides a quick status of the interfaces on the router, including their IP address, Layer 2 status, and Layer 3 status.

 

#6: config terminal, enable, interface, and router

Cisco routers have different modes where only certain things can be shown or certain things can be changed. Being able to move between these modes is critical to successfully configuring the router.

 

For example, when logging in, you start off at the user mode (where the prompt looks like >). From there, you type enable to move to privileged mode (where the prompt looks like #). In privileged mode, you can show anything but not make changes. Next, type config terminal (or config t) to go to global configuration mode (where the prompt looks like router(config)# ). From here, you can change global parameters. To change a parameter on an interface (like the IP address), go to interface configuration mode with the interface command (where the prompt looks like router(config-if)#). Also from the global configuration mode, you can go into router configuration using the router {protocol} command. To exit from a mode, type exit.

 

#7: no shutdown

The no shutdown command enables an interface (brings it up). This command must be used in interface configuration mode. It is useful for new interfaces and for troubleshooting. When you’re having trouble with an interface, you may want to try a shut and no shut. Of course, to bring the interface down, reverse the command and just say shutdown. This command can be abbreviatedno shut.

 

#8: show ip route

The show ip route command is used to show the router’s routing table. This is the list of all networks that the router can reach, their metric (the router’s preference for them), and how to get there. This command can be abbreviated shipro and can have parameters after it, like shiproospffor all OSPF routers. To clear the routing table of all routes, you do clear ip route *. To clear it of just one route, do clear ip route 1.1.1.1 for clearing out that particular network.

 

#9: show version

The show version command gives you the router’s configuration register (essentially, the router’s firmware settings for booting up), the last time the router was booted, the version of the IOS, the name of the IOS file, the model of the router, and the router’s amount of RAM and Flash. This command can be abbreviated shver.

 

#10: debug

The debug command has many options and does not work by itself. It provides detailed debugging output on a certain application, protocol, or service. For example, debug ip route will tell you every time a router is added to or removed from the router.

 

More Cisco IOS Commands Tips:

Top Five Cisco IOS Commands Every Network Admin Should Know

How to Configure IPSEC Encryption with the Cisco IOS?

Configuring Local Username Database in Cisco IOS

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How to Select Your Cisco Products?

July 30 2012 , Written by Cisco & Cisco Router, Network Switch Published on #Cisco & Cisco Network

 

Today, WAN technologies most often take advantage of high-speed connections, such as T-1 and E-1. Additional WAN technologies exist, including Frame Relay, ISDN, and dial-up asynchronous connections. ISDN or dial-up is used if infrequent connection is made. If a connection is used for more than two to four hours, you should use a Frame Relay or a leased line. Based on the different services available through the service provider, you can select Cisco products that can fulfill your office requirements.Select-Your-Cisco-Products.jpg

Selecting Hubs

Cisco has various hub products. You can select hubs according to the type of connection required. Higher-end hubs offer network management port and console connections, middle-end hubs offer both 10 Mbps and 100 Mbps auto-sensing connections, and the lower-end hubs offer only 10 Mbps connections. Examples of fast hub series of Cisco are Cisco Fh100, Cisco Fh200, Cisco Fh300, and Cisco Fh400. Examples of micro hub series are Cisco MH1500 and Cisco MH1528.

Selecting Routers

Routers are the most popular Cisco products. To select a router, you must first know the port density and the interface speed required based on the LAN or WAN technologies used. In addition, you must identify the capacity and performance requirements of your business. The cost of the router varies according to the features you select.

Selecting Switches

A switch can be used instead of a hub in newer networks. Most switches are configured to limit collision domains, which often provides a limited security feature because users will not be able to sniff traffic as easily as in a standard hub-based network. This feature can cause confusion when using a network sniffer to analyze traffic. It is possible, however, to analyze packets on a switched network by enabling mirroring on the switch, or by using a dedicated port that allows authorized users to view all network traffic. It is important to consider whether you need 10, 100, or 1000 Mbps for each desktop or to connect between switches. To select a switch, you must consider various issues, such as business requirements, requirements for inter-switch links and trunking, port density, and type of user interface.

Product Selection Criteria

When selecting the right products for any network environment, keep the following considerations in mind:

  • Will the device be used as a core device, distribution device, or access device?
  • Does the device provide the functions that your business requires?
  • Does the device have adequate number of ports and the right mix of interfaces as required by your business?
  • Do you have to pay a lot for installing the device or can it be easily installed?
  • Can the device be centrally managed from an SNMP Management station or do you have to physically access the device to manage it?
  • Is the migration path easy?
  • How well does the device handle redundancy requirements?
  • Do you have to change your existing infrastructure, such as cabling or existing devices, to install the new device? You may use the Cisco’s official website to gather more information to select products based on your requirements.

 

More Info and Tips of Selecting Cisco Hardware

How to select a very right router for home or business?

Buy used cisco hardware vs. new cisco equipment

 

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