Common Types of Ethernet

April 29, 2013

Here is a simlpe table to help you with your CCENT and CCNA exams, remember these!!

TYPE SPEED NAME STANDARD LENGTH
Ethernet 10Mbps 10BaseT IEEE 802.3 Copper 100m
Fast Ethernet 100Mbps 100BaseTX IEEE 802.3a Copper 100m
Gigabit Ethernet 1000Mbps 1000Base SX

1000Base LX

IEEE 802.3e Fibre 550m

Fibre 5km

Gigabit Ethernet 1000Mbps 1000BaseT IEEE 802.3ab Copper 100m

 

 


Console and VTY Line Passwords

April 29, 2013

Console Passwords:

To protect the console line with a password you will need to configure the following commands:

in (config) mode enter line con 0 to get to the line configuration mode

type in password (password) 

login

that’s it

once configured you have 3 attempts to get the correct password before it starts again and remember the password you enter is case sensitive.

VTY Password Setup:

When configuring Telnet on CISCO devices you must remember to setup a password on the VTY lines, with a password set on those VTY lines Telnet is impossible.

Get to global configuration prompt

type line vty 0 4  (range command)

Password (Password)

Login

That’s it

by default when you login via Telnet you will be put into USER EXEC mode


The IP Packet

April 28, 2013

I found this while browsing youtube and i actually remember watching it at TAFE years ago. It really isn’t that bad in explaining the basics of the router, switch, proxy and firewall. It does however have some dated information but the underlying fundamentals which make our TCP/IP networks function are all there. Take a look and become a Packet.

[youtube http://www.youtube.com/watch?v=TbaaMQVYMYQ&w=420&h=315]


Port Security

April 28, 2013

Switches examine the source MAC address of the received frame, switches can take a few possible options if it discovers that the incoming MAC address on that port is NOT SECURE.

  •  shutdown (the switch shuts down the port and sends a log message and drops the frame/s , also the interface status will read err-disabled you have to run a no shutdown to open the port again) ON BY DEFAULT
  • restrict (drops the frames and transmits a log message but does not shutdown the port)
  • protect (only drops the frames)

When configuring Port security and the source MAC address is unknown switchport port-security mac-address sticky can be used and the switch will use the first mac address learned as the Secure MAC address

 


Some Sunday Humour

April 28, 2013

Below is a video i came across when on DIGG, it’s a hilarious mash up of a 1993 computer tutorial but it’s dead serious take a look.

[youtube http://www.youtube.com/watch?v=6hradnkP5bk&w=420&h=315]

 

Read the article that i found here….


Basic Switch Security

April 28, 2013

Cisco Switch Defaults

  • All cisco switch ports are open by (DEFAULT)
  • Attempting to trunk (DEFAULT)
  • Remember all ports are in VLAN1

Best practice habits should include

  • Close Unused ports (shutdown command)
  • Stop the port from trunking with (switchport mode access command)
  • Place all unused Ports into an unused VLAN

Remember the switches should be locked away in a secure room and or a cabinet

 


Basic Types of Topologies

April 27, 2013

Toplogies 101, this guy nails it


CCNA Certification Changes 2013 Summary

April 27, 2013

For all those interested in the ICND1 and ICND2 exam changes, here is a good overview of it all.


Spanning Tree Protocol (STP)

April 27, 2013

Switching loops form when multiple paths exist, when a frame is sent and the the frame travels between the switches and never ends up reaching it’s final destination.

STP is used to prevent switching loops and is on by default, it determines a loop free path and ports that are not on the path are put into a blocking mode. If the best path is no longer available STP will calculate a new “path” and ports on that path that where blocked are brought out of the blocking mode.

NB. the shortest physical path is not the best, STP looks at the speed of the links

STP Quick Overview

  • On by default
  • Used to prevent switching loops

 

STP


Introduction to VLANS

April 27, 2013

A continuous generation of broadcasts on a network is called a broadcast storm, this will use the switches resources to the point of breakdown.

By default a switch is setup to use one broadcast domain, to mitigate this, creating more broadcast domains via creating new VLANS, Cisco switches are out of the box configured using VLAN1 named default.

Segmenting the networking by creating a new VLAN , only those hosts on the same VLAN will be able to communicate,connectivity to another VLAN is not possible without the implementation of a L3 device (eg Router)

Read more from Wikipedia on VLANS here