Before diving into a new technology, it is always useful to understand the previous generation of technology, what the limitations where, and how the new technology intends to overcome them. In this post, let’s look at what some of the
Design Considerations for North/South Flows in the Data Center
Traditional data centers have been built by using standard switches and running Spanning Tree (STP). STP blocks redundant links and builds a loop-free tree which is rooted at the STP root. This kind of topology wastes a lot of links
STP Notes for CCDE
These are my study notes for CCDE based on “CCIE Routing and Switching v5.0 Official Cert Guide, Volume 1, Fifth Edition” and “Designing Cisco Network Service Architectures (ARCH) Foundation Learning Guide: (CCDP ARCH 642-874), Third Edition“, “INE – Understanding MSTP”
Ethernet, STP, Topology change and the behaviour of Ethernet
Introduction This post is inspired by a post at IEOC about Uplinkfast and TCN which can be found here. Before we get to those parts, let’s recap how Ethernet and STP work together. Spanning Tree The Spanning Tree Algorithm builds
Cisco Flex link
Introduction Flex link is a Cisco solution which replaces STP in certain network topologies. It works by detecting link down on a primary interface and then bringing up the backup interface that has been defined as backup. It is most
Network Campus Design
Introduction Modern networks need to be enabled for voice and video. These applications do not tolerate a lot of loss before quality becomes unacceptable. This requires us to build networks that are scalable, resilient and converge quickly. This post will
Detecting Network Failure
Introduction In todays networks, reliability is critical. Reliability needs to be high and convergence needs to be fast. There are several ways of detecting network failure but not all of them scale. This post takes a look at different methods
STP session up @ CLN
Hi, I’m done with the two Spanning Tree Protocol webinars at the Cisco Learning Network. You can find them here. They are located under the Routing&Switching section. Now on to CCDE studies!
STP convergence – MST
In the comments I received a wish to compare RPVST+ with MST. RPVST+ is Ciscos proprietary STP running one instance per VLAN over 802.1Q trunks. MST is an industry standard which can run multiple instances but not one per VLAN.
Spanning tree convergence
Someone asked the other day how fast STP converges depending on PVST+ or RPVST+ or MST is running. Usually the answer for PVST+ is 30-50 seconds and for RPVST+ it’s fast, maybe less than a second. I thought I would