November 16th, 2007
After configuring your switch with Vlans you notice that something is wrong.
I will give you a simple guide to troubleshoot Vlans and make things work again.
- First check for Layer 1 and Layer 2 issues
- Is the cable plugged into the correct port?
- Is the link light on, and if so, what color is it? (If the led has a green color, it means that the switch port is in the forwarding state, if the port led has a yellow color the port is in the blocking state and if the port has a yellow blinking led, it is in the error state.
- We can use the Switch# show interface command to confirm link state
- Check the duplex mode
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November 14th, 2007
With this article I will go you through the configuration of enabling the web interface of your router.
Before showing you the commands, that are quite simple, I will explain what we will achieve with them.
Enabling an HTTP server on the router allowing the administrator by using any web browser to configure the router by pointing to the IP address of the server.
Syntax of the Commands:
Router(config)#ip http server
Now if you wish to enable the web interface in a non default port (The default port is 80) you can use the following command:
Router(config)#ip http port [port number]
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November 12th, 2007
Voice over IP (VoIP) is a major networking application and nowadays is appearing everywhere. VoIP is running over common high speed connections as: Ethernet, Frame Relay, ISDN, ATM, DSL, Cable and other.
With the VoIP technology we can transmit the analog voice signals of our telephone, through the traditional data network. This technology works by encoding analog voice signals into IP packets. These packets are sent across the data network and reassembled and decoded at the other end back to analog signal.
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November 7th, 2007
If you want to discover all the active hosts on your subnet from your routers console, you can perform a ping in the broadcast address of your subnet. Keep in mind that all the active nodes on your subnet should respond to that ping. As a tip I can tell you that this kind of ping will only work in privileged exec mode.
For example if you use the subnet 10.1.1.0 /24 the broadcast address is 10.1.1.255
From privileged mode perform a ping like this:
Router#ping 10.1.1.255
A “list” with all the active nodes should appear.
Another command that you can use to find out with witch hosts has the router communicated is
Router#show ip arp
You can use this useful type of ping for many types of things, for example to check how many computers are connected on a wireless network. Till our next article, stay tuned.
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Posted in General Networking | 19 Comments »
November 5th, 2007
In this article I will give you three useful commands for setting up your router’s clock.
If you are wondering why the router’s clock is important, just think the syslog messages. Every syslog message has the time that the event occurred. Imagine a hacking attempt that has been tracked by your syslog, if the clock of your router is not configured properly, you can’t find out when the attack took place.
Now let’s start with the commands.
Clock set
Clock set hh:mm:ss day month year
This command manually sets the router’s clock. The time is specified in terms of a 24 hour clock and the year must be in a four digit notation for example 2000.
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November 2nd, 2007
Hello again, after getting some feedback from the Computer Problems article, i thought i should write an article about the next big decision you will have to make.
Situation is like this: You’re enjoying with your afternoon with your friends having fun. Your cellphone rings and once again it’s the mr. IWontSpendAMinuteFixingMyComputerCauseIKnowPeopleWhoWillDoItForMe, starting once again the usual conversation:
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October 30th, 2007
The Mozilla Corp. has announced the development of a completely functional Firefox web browser for mobile phones.
According to a statement made by Mike Schroepfer, vice-president of the department of Mozilla’s engineers, the official publication of Firefox for mobile phones will be released at the end of 2008. He has also announced the development of Firefox 3 for PCs.
The mobile Firefox will probably have the capability of accepting themes and support XUL.
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October 27th, 2007
As you can guess correctly this is not an article purely for networks, but it concerns me for quite some time so i would be more than happy to get some feedback on it.
I am into computers for more than 10 years and i think many of you reading this blog, would be using computers for more than 5 because after all, you can’t say: Hmm computers might seem something good. Let me start using them! And the next day you’ve come upon a specialized networks blog and start reading it:)
So, i was thinking… What’s the problem with today’s computer users?
I’ve come up to this question because it seems that the average person that uses a computer doesn’t have:
- Patience
- Passion to make things happen
- Appetite for knowledge
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October 24th, 2007
In this article I will show you how to configure an Ip address and a default gateway in your manageable switch.
But first things first,
Why is an Ip address and default gateway needed in the switch?
After all switches are OSI Layer 2 devices that care only about MAC addresses.
The modern switches are manageable and support extra features than normal old fashion switches. This features include the support of TCP/IP applications like ping, telnet, trace route etc. For example, if you want to telnet or ping a switch, the switch must have an Ip configured. Also, if you want to execute ping or telnet to a device in another subnet the switch must have a default gateway configured.
Now let’s see the configuration for a 2950 series cisco switch.
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October 22nd, 2007
Many times a lot of us who use laptops or desktop computers which are equipped with wireless network cards, have tried to scan an area for available wireless access points. We usually use the default wireless network scanner of the Windows operating system.
But is this the most efficient tool for this job?
Surely not.
There is a tool, not quite widespread, called Network Stumbler which is much more effective than the default windows scanner. The network stumbler is a wireless network scanner that supports many different chipsets of wireless network cards as Lucent, Dell True Mobile, Compaq WL 110, Elsa Airlancer and several others.
I guess that many of you are already familiar with it. For those who haven’t heard of it before let’s see why network stumbler is better than the default windows wireless scanner.
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