Interesting Links

Probably a category which is found in a lot of blogs, but the more I think about it, the more I like this kind of post. My google reader blog list grows and grows and there are those posts I’d like to save somewhere, so I could either make myself a (some when) blown up link list or why not share it with others, and create a category on my blog for it, so I got a full searchable link archive?

I don’t know yet how often I will post such an article, so lets see how it will evolve 🙂

IPExperts Cisco’s STP Toolkit

Overview about the STP Enhancements from Cisco

Cisco was not going to sit and wait around for the standards bodies to enhance Spanning-Tree Protocol so that it would converge faster and be more safe to implement. Instead, Cisco has been hard at work creating tools that could improve the protocol. Here is some review about these various tools.

IPExperts BPDUFilter in Action

Article about the Spanning-Tree Protocol BPDUFilter feature

What if you have the rare circumstance that you want to prevent a port on your switch from sending BPDUs? This is one of the jobs that can be accomplished by BPDUFilter. You need to be very careful with this feature in the lab exam, as well as your production network, of course. That is because this feature not only prevents the sending of BPDUs by a port, but it can also result in a port ignoring BPDUs that are received. Of course, this can lead to a Layer 2 loop in your environment.

IPExperts RootGuard in Action

Article about RootGuard, how it works, is configured and tested:

Many Layer 2 implementations these days have Cisco switches facing customers or partners and there is a risk of inadvertent or malicious Spanning Tree Topology manipulations. Remember from previous posts that STP will reconvergence the topology based on the receipt of what we term superior BPDUs. The Root Guard feature guards a port or ports against such an occurrence by moving the port into a root inconsistent state (effectively disabled) based on the receipt of one of these superior BPDUs.

Cisco on How to properly and safely collect debugs on an IOS router

Actually written for Voice debugs, but if you change the debug commands to something else, it can be useful for other debugs too.

Three Articles on Routing-Bits about Cisco’s OTV(Overlay Transport Virtualization):
Cisco OTV (Part I)
Cisco OTV (Part II)
Cisco OTV (Part III)

OTV(Overlay Transport Virtualization) is a technology that provide layer2 extension capabilities between different data centers. In its most simplest form OTV is a new DCI (Data Center Interconnect) technology that routes MAC-based information by encapsulating traffic in normal IP packets for transit.


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