Daily Archives: April 7, 2012

Routers and Switches Review

Review of IOS for Routers and Switch

  • Subinterface – Commands that configure multiple virtual interfaces on a single physical interface.
  • Router – Commands that configure an IP routing protocol.

Medium Sized Switched Network Construction

  • VLAN is a logical broadcast domain that can span multiple physical segments.
  • Trunk ports carry ALL VLAN traffic
  • VLAN = Broadcast domain = subnet
  • A native VLAN carries all UNTAGGED frames.
  • VTP domain is one or several switches sharing the same VTP environment.

VTP Modes:

Server: VTP Messages are propagated over all trunk links.

Transparent: Changes affect the local switch only and does not propagate.  Forwards advertisements but does not sync with other devices..

Clients: Advertisements are forwarded and synchronise  with server switches.

VTP advertisements are flooded throughout the management domain, every 5 minutes or whenever a change is made.


Higher revision number -> more current information

To change the VTP config number:

  • Change the VTP domain name or change it back
  • Change to VTP transparent mode then back

VTP Pruning: Restricts the flow of traffic only to ports within the VLAN’s that the traffic is destined for -> Server mode only.

A trunk port cannot be a secure port.


  • 1 Native VLAN
  • 2 – 1001 Normal VLAN Range
  • 1002 – 1005 Reserved for Token Ring and FDDI
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Since I passed the CCENT last November I have been busy but I have also been lazy.  No excuses, now it is time to get serious, head down bum up in study for the CCNA.

One thing I find difficult about working in the IT industry is that it is very hard to stay focused on a single technology or technology track because there are so many interesting technologies out there that catch our attention.  I guess for most of us it comes down to discipline, for example lately I have been listening to some security related podcasts and found that I have the overwhelming urge to research penetration testing tools, and security related Linux distros, IDS/IPS etc.

Its easy to get caught up, drop what your doing and concentrate on something more interesting, unfortunately in my opinion this only results in a very minimal overview of the subject resulting in the old jack of all trades and master of none.  I have been thinking about this a lot lately with my own studies and have come to the realisation that if I don’t have a good grounding in the basics of routing and switching it will be a lot harder when it comes to studying other technologies like Voice or Security for example.

With this in mind, now is the time to knuckle down and get the CCNA out of the way with a view to moving on to more interesting technologies/tracks.  I have read the CCNA press book from cover to cover and I will be posting the hard written notes I made from that as a way to reinforce the material.  After this I will post my study plan for the next few weeks leading up to the exam date.

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