Some of you have noticed that I've started using new icons in my topology drawings lately. I recently discovered a wealth of impressive Visio shapes provided for free by the good folks at VSD Grafx, who do custom Visio shape development. They offer three identical sets of 110 generic network shapes (one set each in blue, green, and grey) of impressive quality. Here are just a handful.

These shapes are 100% vector images, meaning that they scale perfectly to any degree.
Although they aren't typically of use for topology drawings, VSD Grafx also offers stencil sets of true-to-life shapes of everything from desktop printers to a conference room complete with faceless attendees. The quality of these shapes is nothing short of amazing. Included below are just a few random samples.

The stencil sets are available at VisioCafe: just grab the full set .zip file to get all of them.
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Now that the community lab has been equipped with a Catalyst 3560, I have finally been able to write about private VLANs (which are supported only on Catalyst 3560 and higher switches). This article discusses the concept of private VLANs and includes a basic configuration example, with more complex configurations deferred for future articles.
Private VLANs were developed to provide the ability to isolate end hosts at layer two. To understand the motivation behind this feature, consider a colocation environment in which the network operator must connect servers belonging to different customers to the Internet. These servers must all be able to reach their first-hop router, but for security reasons, servers belonging to one customer must not be able to communicate with servers belonging to another. An obvious design solution for these requirements is to place each customer's servers in a separate VLAN, which also requires the assignment of a separate IP subnet per customer (even if they have only one server).

This approach wastes both VLAN IDs and IP address space. Private VLANs were introduced as a more elegant alternative, allowing multiple devices to reside in the same IP subnet, yet remain isolated from one another at layer two.

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