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VLAN cheat sheet

By stretch | Monday, April 14, 2008 at 11:57 a.m. UTC

In following the VLAN theme from my last post, I present to you a new cheat sheet on VLANs and trunking (PDF link):


I started work on this cheat sheet unsure if I'd be able to fill an entire page with material, but after a bit of study I was reminded DTP and VTP were relevant and should be included. Some people have a hard time remembering which is which, and understandably so. Here's a quick summary to complement the cheat sheet:

  • Dynamic Trunking Protocol (DTP) is used to automatically establish a VLAN trunk between two ports configured to do so. Best practice is to configure trunk ports as trunk and access port as access (complicated, eh?). This is to prevent a malicious user from emulating a trunking switch and achieving VLAN traversal.
  • VLAN Trunking Protocol (VTP) is used to automatically propagate VLAN information from one server switch to multiple client switches. The main benefit in running VTP is to eliminate the administrative burden of manually creating or removing VLANs on a number of switches. However, as with all "convenience" protocols, it should only be enabled if you have a legitimate need for it. Switches can be configured not to participate in VTP by setting them to transparent mode.

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