CCNP Security Career

Like any Cisco professional level exam, the CCNP SWITCH (642-813) exam covers a number of different topics that you are expected to be familiar with. For the SWITCH exam, the main points are features that are run on a number of the Cisco switching platforms. The purpose of this article is to review a few of the more difficult SWITCH topics and how to prepare for them; this list is of course rather subjective.
The five topics I selected for this article are based on an informal review of the SWITCH exam topics and include the Spanning Tree Protocol (STP), Switch Virtual Interface (SVI), Virtual LANs (VLAN), VLAN Trunking Protocol (VTP) and Switch port security.

Spanning Tree Protocol (STP)

The thing about studying spanning tree is that it really depends on how deep you are looking to understand it. A good amount of the STP topics covered on most exams can be learned without doing an extensive amount of STP testing on live equipment. This includes a general understanding of what STP does (prevents loops) and generally how this is done in terms of root switches and forwarding and blocking links. A true understanding of how STP really works is needed for those looking to get into a position where the configuration of a switched network is a main part of their duties.

CCNP Security professional Definition:  

To understand STP, you must take a number of Cisco switches (cheap ones work, 2950s are really cheap) connect them together and modify the different spanning tree priorities to see how the different paths are calculated depending on the switch acting as the root switch. It is best to do this following a single VLAN at a time at first to ensure a good understanding before looking at how STP works over multiple VLANs (this is assuming default Cisco VLAN behavior).

It is also important to understand the differences between STP and Rapid STP (RSTP). RSTP was developed as a standard to accelerate the state changes of switchports when a change occurs; one common complaint about STP is that an interface can take a long time to transition from blocking to forwarding states. This should also be simulated in the lab and is supported on 2950s as well.
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