What is bridge ID priority?
Each switch has a unique bridge identifier (bridge ID), that determines the selection of the root switch. The bridge ID is an 8-byte field that is composed of two sub fields: The value for the priority ranges from 0 to 61440 in steps of 4096. The default value for the priority is 32768.
What is the bridge priority value range?
0 to 61440
Bridge Priority The default priority value for all Cisco switches is 32768. The range is 0 to 61440 in increments of 4096.
How does STP calculate bridge ID?
The root bridge of the spanning tree is the bridge with the smallest (lowest) bridge ID. Each bridge has a configurable priority number and a MAC address; the bridge ID is the concatenation of the bridge priority and the MAC address. For example, the ID of a bridge with priority 32768 and MAC 0200.0000.
What is the advantage of Pvst+?
PVST+ requires fewer CPU cycles for all the switches in the network. PVST+ reduces bandwidth consumption compared to traditional implementations of STP that use CST. PVST+ optimizes performance on the network through autoselection of the root bridge. PVST+ optimizes performance on the network through load sharing.
What is the maximum value for the bridge priority in STP?
61440
Then the Bridge Priority can take values from 0 to 61440 in increments of 4096. Regards! If you add up the decimal values of the 4 left bits, you get 61440 as resulat. So 61440 is the highest possible value if all 4 bits are set to 1.
What is port ID in STP?
Port ID is a logical interface identifier configured to participate in the STP instance. AFAIK it consists of port priority and port index. If BPDUs have the same Root Bridge ID, the same path cost to the Root and the same Sending Bridge ID (multiple links between two switches) then Port ID is used as a tie-breaker.
How do I change the priority of a STP bridge?
To ensure that a switch has the lowest bridge priority value, use the spanning-tree vlan vlan-id root primary command in global configuration mode. The priority for the switch is set to the predefined value of 24,576 or to the highest multiple of 4096 less than the lowest bridge priority detected on the network.
Should you disable STP?
You really, really do not want to disable STP where you connect switches to other switches. That is the entire purpose of STP. If you disable STP, and there is a problem, it will really be too late because your entire network could crash when you notice it, and recovering from a broadcast storm is no fun at all.
What is the bridge priority ( switch priority ) value?
The Bridge Priority (Switch Priority) value is used to find the Bridge ID (Swtich ID). The Bridge ID (Swtich ID) is made from two values. • The Switch Priority, which is a numerical value defined by IEEE 802.1D, which is equal to 32,768 by default. • The MAC Address of the Switch.
What’s the default STP priority for root bridge?
Default STP priority is 32768. The lower the priority the more likely the switch is to be come the root bridge. However you normally have to do STP in incerments of 4096 so you would not be able to allocate a priority of 1 to a switch.
What is the extended system ID in STP?
The Extended System ID is a value of 1 to 4095 corresponding to the respective VLAN participating in STP. The Bridge Priority increments in blocks of 4096 to allow the System ID Extension to squeeze in between each increment.
How is the system ID added to the bridge ID?
By default, Cisco’s Per-VLAN Spanning-Tree Plus (PVST+) adds this System ID Extension (sys-id-ext) to the Bridge Priority. The two values ( Bridge Priority + System ID Extension) together make up the Bridge ID used to elect the Root Bridge.