Blog Archives

3 reasons for the occurrences of the RSTP backup role.

Alternate title: Monday morning musing on the RSTP backup port role. Arguably the most misunderstood role in RSTP is the so called “backup” port role. The mantra of this role is typically that this type of port should not been

Posted in Certification, Switching

Snooping around with IGMP Snooping.

Posted in Switching

RE: Simple STP Problem 80% Get Wrong

I have had some very interesting feedback (mostly of disbelief at my answer) including from a very popular certification prep vendor’s technical editor about this post.  As a cross reference see my other post titled “Simple STP Problem 80% Get

Posted in Education, Switching

Simple STP Problem 80% Get Wrong

The 80% number is just a shot in the dark guess it may be lower or higher but I personally have not had anyone answer this question correctly.  Looking at various documentation the 4th STP tie breaker is not well understood.

Posted in Education, Switching

TRILL versus vPC

I was asked by several engineers last week if “TRILL was better than vPC.”  I appreciate being asked the question since, apparently, I was viewed as knowledgeable enough on the subject to give a reasonably accurate answer.  In short, comparing

Posted in Switching

Spanning-tree Conundrum

The following depicts a basic L2 topology with Cisco switches running default configuration of STP.  S1 has been elected the root bridge for all VLANs.  The incoming port costs have been labeled on several of the links. 1.  Which link

Posted in Switching

Quote from Radia Perlman.

A profound thought: “But the world would be a better place if more engineers, like me, hated technology. The stuff I design, if I’m successful, nobody will ever notice. Things will just work, and be self-managing. Though, I’ve learned that some

Posted in Education, Switching
Charles Stizza

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  • RFC 8196: IS-IS Autoconfiguration July 20, 2017
    Finally a group of engineers figured out it’s a good idea to make things less complex instead of heaping layers of complexity on top of already-complex kludges.RFC 8196 specifies default values and extensions to IS-IS that make it a true plug-and-play routing protocol. I wonder when we’ll see it implemented now that everyone is obsessed with intent-based hyp […]
    Ivan Pepelnjak