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.