Storm-control and unicast-flooding

When a broadcast storm occurs, even with STP enabled, there is another option to protect your network from broadcast flooding. This method is called storm-control. The technics of this protocol are simple:

Stom control configuration is based on a per-port bases and storm control can be enabled for broadcasts, unicasts and/or multicasts. When configuring stormcontrol, you have to specify the rising and falling values: the rising value is the value on which an action should occur (rate-limit the traffic to this value, err-disable this port or send a SNMP trap). The rising value is the value on which the action will be undone.


Spanning-tree root guard, BPDU guard and loop guard

This is another (short) post about three more important features of spanning-tree, as discussed on my previous blog.

Spanning-tree root guard is useful in avoiding layer 2 loops during network anomalies. Root guard forces an interface to become a designated port to prevent switches from becoming a root switch.



My first day of study: it’s a spanning-tree day! Most of the information is a fresh-up from the CCNP course, but still very usefull to know. Below a summary of some key-parts of spanning-tree, rapid-spanning-tree and mst.   

Spanning-tree bridge ID format   

The “old” version of spanning-tree, also known as 802.1d, uses the following bridge ID format:   


The priority is a 2 bytes (16 bits) field with all possible values between 0 and 65535. The MAC address is used as a tiebraker.   


Study blog

This is my first blog on this new blog site. I’ m quite happy with the looks and feels of this WordPress installation: it’s so easy to start and I realized that I should have been started a blog ages ago…

This new year, 2011, is just a few days old and I’ve decided to begin a ‘new’ study course: CCIE Routing & Switching. There is a lot of information about this topic on the internet: other blogs, mail groups, news groups, but I would like to share all study-related topics I’m going to experience in the upcoming months.