Blog - Month: October 2016

As a CCNA candidate you must be familiar with the functions and configuration of trunk links.
In brief a trunk link is any connection between two switches where there is the need to carry traffic for multiple vlans.

When a switch sends traffic out of one of it’s switch ports belonging to a vlan across to another switch it must mark the frame as being a member of that originating vlan on the sending switch so that the receiving switch can determine into which vlan to place the frame.

In the CCNA there are various methods of trunk link configuration that you must know and understand.

The first method of trunk link configuration you must know for the CCNA is the mode known as dynamic desirable. In this mode the port will take it upon itself to negotiate with the peer connecting port to become a trunk link. This Protocol is known as DTP (Dynamic Trunking Protocol), in the CCNA the way in which DTP operates is expected.
Switch(config-if)#switchport mode dynamic auto

As a CCNA candidate you have to know that a port set to DTP (Default on many Cisco Switches) will always try to become a trunk, periodically the port set to Dynamic Desirable will send out a DTP frame, if it receives a DTP frame in return then at that point the two ports will become trunks.

The second method for port setting is known as Dynamic Auto, another topic that as a CCNA student you must know and experiment with. Unlike Dynamic Desirable, the Auto mode is in a passive state and will not issue DTP frames until it receives a DTP frame from an attached port, at which point the auto mode port will reply with it’s own DTP frame and the two ports will then become trunk links and carry all vlans by default.

Switch(config-if)#switchport mode dynamic auto
The third method which as a CCNA candidate you must be aware of is the generally preferred method and is called simply “Trunk”. In this particular mode the port is going to become a static trunk regardless how the other end is set.

Switch(config-if)#switchport mode trunk
When setting a port to “Trunk” many CCNA students believe that DTP is disabled, this is not the case, to disable DTP one must run an exclusive command under the interface prompt, his command is

Switch(config-if)#switchport nonegociate

It is advisable that all ports connecting switches together are set for static trunking and that DTP is turned off.
The point of turning off DTP is so that is no other Cisco device (By somebody wanting view your traffic) to is connected to your switch they will not inadvertently negotiate a trunk link, at which point all of your broadcast traffic from all vlans is visible

If you’re locked out of a router due to not knowing the password don’t worry you can easily get back into the router by changing the configuration register.

The configuration register (CR) is a 16bit number (2 Bytes) written into NVRAM that is used to tell the router where and how to boot, by default the CR is set to load the IOS from flash followed by getting the startup file from NVRAM.is whether to use the contents of NVRAM to load a router configuration.

The default setting for the configuration value on the Cisco router is 0x2102, this setting tells the router to boot normally, i.e take the IOS from Flash and find the Startup configuration from NVRAM.

Below is a table detailing the software configuration meanings
Bit Number Hex Meaning
• 00-03 0x0000-0x000F Boots Field Parameters:
• 0x0000 – Stays at the system bootstrap prompt.
• 0x0001 – Boots the first system image in onboard Flash memory (EPROM).
• 0x0002-0x000F- Specifies a default netboot filename. Enables boot system commands that override the default netboot filename.
• 06 0x0040 – Ignore NVRAM contents
• 07 0x0080 – Disable boot messages
• 08 0x0100 – Break disabled
• 10 0x0400 – IP broadcast with all zeros
• 5,11,12 0x0020, 0x0800, 0x1000 • Console line speed
• 13 0x2000 – Boots default ROM software if network boot fails
• 14 0x4000 – IP broadcasts do not have net numbers
• 15 0x8000 – Enables diagnostic messages
• Ignores NVRAM contents

Step 1: To view the current Configuration Register settings run the command ‘show version’
Here are the main steps to password recovery:

R1# show version | sec Conf
Configuration register is 0x2102

Step 2: Lets go through the steps to recover the router, first of all you need to have a console connection to the router since you will boot the router and during the initial first few moments of the routers boot cycle you will interrupt the boot sequence by performing a break, breaking the boot sequence will take the router into ROM monitor mode.

Your first step is to boot the router and perform a break. This is usually done by pressing the
Ctrl+Break key combination when using HyperTerminal or Alt+B with Tera Term while the router first reboots.

After you’ve performed a break, you should see something like this for a 1841 series router

%SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload Command.
System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2006 by cisco Systems, Inc.
PLD version 0x10
GIO ASIC version 0x127
c1841 platform with 131072 Kbytes of main memory
Main memory is configured to 64 bit mode with parity disabled
rommon 1 >

At this point, you will be at the rommon 1> prompt, which is called ROM monitor mode.

Step 2: Change the configuration register by using the config-register command. To turn on bit 6, use the configuration register value 0x2142. Remember that if you change the configuration register to 0x2142, the startup-config will be bypassed and the router will load into setup mode.

rommon 1 > confreg 0x2142

You must reset or power cycle for new config to take effect

rommon 2 > reset

Step 3: The router will reload and ask if you want to use setup mode (because no startup-config is used). Answer no to entering setup mode, press Enter to go into user mode, and then type enable to go into privileged mode.

Step 4: Now you’re past the point where you would need to enter the user-mode and privileged-mode
passwords in a router. Copy the startup-config file to the running-config file:

router# copy startup-config running-config

The configuration is now running in random access memory (RAM), and you’re in privileged
mode, meaning that you can now view and change the configuration. But you can’t view the
enable secret setting for the password since it is encrypted. To change the password, do this:

router# config t
router(conf)# enable secret cisco

Step 5: After you’re finished changing passwords, set the configuration register back to the default
value with the config-register command:

router(conf)# config-register 0x2102

Finally, save the new configuration with a copy running-config startup-config and reload the router.

If we had a pound every time we were asked “Why are you so cheap?” we could close our doors and retire.

We wish we could claim that we started the whole discounting revolution but that accolade has to go to the likes of Southwest airlines in America and Ryanair in the UK, they led the way. They showed the world that charging high prices did not necessarily justify the product, but by offering low prices they proved that compromises did not have to be made in safety or the quality of the aircraft which they operated
But how is it possible that Ryanair and Easyjet can fly you across Europe for £1. We like to call it “Economic Intelligence”.

We apply the same Economic Intelligence to our business, for example all Commsupport office staff other than instructors all work remotely to reduce unnecessary office overhead costs, we run an almost 99% paperless office and negotiate hard with all our suppliers down to the very last last penny on all of our purchases so that we can pass the savings onto our students. Like Tescos’ say “every little helps”, everything helps down to helping ourselves to the free pens at Barclays bank.

We also get asked “do you make any money?” or “how do you make money?”, our response is, we of course do make a profit otherwise why would we bother; as much as we love teaching we do have to live, air is free but not very filling.

We say don’t worry about how much money we make or how we make a profit the real concern ought to be whether we can deliver the product that we claim to be able to deliver. We have been in business since January 2007 and we have trained over 3000 students with a lot of repeat business, that is testament that quality training can be delivered at rock bottom prices, just see how many copy cat companies our concept has spawned to tell you it can be done.

The question you ought to really be asking is why other training companies feel the need to rip their customers off with high prices and low quality courses, poor material, poorly qualified instructors.

Come to our “Free one day training sessions” so you can try us out before you commit, see the real classes in action. If the likes of Ryanair and EasyJet can make a £30 million pound aircraft pay its way for a quid a flight why can’t we offer a course at the prices we do?