Different Types of Spanning Tree Protocols, Defined Briefly

802.1D and its successor protocols provide loop resolution by managing the physical paths to given network segments. STP enables physical path redundancy while preventing the undesirable effects of active loops in the network.

The first STP, called the DEC STP, was invented in 1985 by Radia Perlman at the Digital Equipment Corporation. In 1990, the IEEE published the first standard for the protocol as 802.1D based on the algorithm designed by Perlman. Subsequent versions were published in 1998 and 2004 incorporating various extensions. 

Why STP Bridge Priority is Configured in increment of 4096

Spanning-tree operation requires that each switch have a unique BID (Bridge ID). In the original 802.1D standard, the BID was composed of the bridge priority and the MAC address of the switch, and all VLANs were represented by a CST, Common Spanning Tree. Because Cisco started to use unique instance in PVST+ PVRST+ for each VLAN STP Process, there came need to provide Unique BID for each separate instance of STP per VLAN. So what Cisco Did! divided the Bridge priority field of 16 bits into two parts, 4 bits for priority and 12 bits for VLAN ID and named it as Extended VLAN ID. Now because only left most  four bits are reserved for Bridge priority, you can only make the combinations of discrete values in increments of 4096 with those bits.

VLAN Ranges Supported by Different Models of Cisco Switches

Depending on the Platform and Software Version, Cisco Catalyst switches support up to 4096 VLANs.

Following data Lists the Cisco Models and VLAN ranges supported by them, also some of the VLAN numbers are reserved and can not be used or modified.

Best Practices for VLAN Design

Following these General Best practices when implementing VLANs can help to design and implement VLANs in a simple, secure and less troubleshooting-requiring Campus Network.

• For the Local VLANs model, it is usually recommended to have only one to three VLANs per access module and limit those VLANs to a couple of access switches and the distribution switches.

What is Difference between Contiguous and Discontiguous Networks With Example

I am trying to Explain both terms in some details with example, and trying to keep them as simple as I can so that you can easily understand the meaning of the terms and differences between them.

Contiguous Network
The Synonyms of the word Contiguous is Continuous that means "connected together so as to form an unbroken sequence in time".