Category: Switching

MAC Addresses of Switches

Ok, this is going to be the first article in a series of articles about the CCIE recertification topics (some, not all..) I’m currently going through to get myself recertified 🙂 And to have some of the base topics handy for the future. As long as Cisco doesn’t change all of them 😉

**Update 8th of October 2010**
As it looks like the information below only works for “older” switches like 3550 and 2950. Newer Switches like 3560, 3750 or 2960 do behave different!

As every Ethernet device, switches do use MAC addresses to address their own interfaces, including the Switch Virtual Interfaces (SVIs). They do use a “base” MAC address for the SVI(s) and increase it by one for every interface, starting with the very first.

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VTP “Specials”

VTP is a nice tool if you have a larger network with a lot of VLANs and modifications, but it also has its dark sides. Im going to show three different scenarios and how VTP behaves in those, the first two might not be a big suprise, neither the third (cause its written in a warning inside the config guide) but maybe it shows why and how VTP is going to behave in those situations. Im going to start with some copy&paste action (why should I write something by myself if there is already a well written text? 🙂 ) from the Cisco Config Guide about VTP and its three modes.

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