What is extended system ID (ESID)?
So IEEE came with the idea of Extended System ID in which they reused a part of the priority field for a unique instance identifier. In Cisco's implementation, this field is populated with the VLAN number the STP/RSTP instance runs in.
What is the extended system ID in PVST?
When you use PVST and other advance mode,the Extented system id come into picture,because the BPDU now have to carry pirority and the VLAN that BPDU belong to and so Extented system id is used,in normal STP Vlan informtion is not required since only one instance is running.
What is spanning tree extended system ID?
So what is Spanning Tree Extended System ID? The Extended System ID is utilized by spanning-tree to include the VLAN ID information inside 16-bit STP Bridge Priority value. Extended System ID is the least significant 12-bits in 16-bit STP Bridge Priority value.
What are the possible values of the system ID extension (sys-ID-ext)?
This means that possible values are: 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768 etc. By default, Cisco’s Per-VLAN Spanning-Tree Plus (PVST+) adds this System ID Extension (sys-id-ext) to the Bridge Priority.
What is the extended system?
Description. The extended system ID is used to specify different bridge identifiers for different RSTP or STP routing instances.
What are the three components of an STP bridge ID?
The three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.
What is root ID and bridge ID?
The bridge ID is the mac-address of the switch you are on. The root ID is the mac-address of the switch that is the root bridge for that vlan. So if the bridge ID and root ID are the same then you are on the root bridge for that vlan.
What is bridge ID?
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. The VLAN ID ranges from 1 to 4096. Copyright © 2010, 2012, Oracle and/or its affiliates.
What additional information is contained in the 12-bit extended system ID of a BPDU?
What additional information is contained in the 12-bit extended system ID of a BPDU? Explanation: The BPDU has three fields; the bridge priority, the extended system ID, and the MAC address. The extended system ID contains 12 bits that identify the VLAN ID.
How is bridge ID calculated?
Path to the root bridge Bridge ID = priority (4 bits) + locally assigned system ID extension (12 bits) + ID [MAC address] (48 bits); the default bridge priority is 32768, and. Port ID = priority (4 bits) + ID (Interface number) (12 bits); the default port priority is 128.
What is STP BPDU guard?
BPDU Guard is a feature that defends the Layer 2 Spanning Tree Protocol (STP) topology against BPDU-related threats and is designed to protect the switching network. The BPDU guard feature must be activated on ports that should not receive BPDUs from connected devices.
What is bridge priority in STP?
The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.
What are BPDU packets?
Acronym for bridge protocol data unit. BPDUs are data messages that are exchanged across the switches within an extended LAN that uses a spanning tree protocol topology. BPDU packets contain information on ports, addresses, priorities and costs and ensure that the data ends up where it was intended to go.
What does BPDU stand for?
bridge protocol data unitA bridge protocol data unit (BPDU) is a data message transmitted across a local area network to detect loops in network topologies. A BPDU contains information regarding ports, switches, port priority and addresses. BPDUs contain the information necessary to configure and maintain spanning tree topology.
What is STP blocking?
STP (Spanning Tree Protocol) makes sure that there are no loops in the network... when a port goes into blocking state that means it's preventing a loop somewhere which is a good thing. There must be some other uplink that is creating a loop which isn't neccessarily a problem unless you didn't intend on it by design.
How does STP elect root port?
STP Root Port SelectionLowest bridge ID (Priority:MAC Address) switch becomes the Root-Bridge.Each non-root bridge should have ONE root port (RP) which is the port having lowest path-cost to Root Bridge.All ports in Root Bridge become Designated Ports (DP)Each segment should have one Designated Port (DP)More items...•
Which one is a component of a bridge ID?
This identity is called the Bridge ID or BID. It is an 8 byte field which is divided into two parts. The first part is a 2-byte Bridge Priority field (which can be configured) while the second part is the 6-byte MAC address of the switch.
How is the root bridge determined in STP?
The root bridge is selected by manually configuring its bridge priority to a low value. 32768 is the default value out of a range from 0 to 61440. If all switches in a single spanning tree have the same bridge priority, the switch with the lowest MAC address will become the root bridge.
Which option identifies the STP bridge priority range?
The default priority is 32768, and additional roots are set below this number. STP increments priority by 4096, so the next priority is 4096 below 32768. The lower the number, the higher the priority.
Which is a type of STP state?
There are five STP switchport states; these are: Disabled - The result of an administrative command that will disable the port. Blocking - When a device is connected, the port will first enter the blocking state. Listening -The switch will listen for and send BPDUs.
What is STP in LAN?
STP is a Layer 2 link management protocol that provides path redundancy while preventing loops in the network. For a Layer 2 Ethernet network to function properly, only one active path can exist between any two stations. Multiple active paths among end stations cause loops in the network. If a loop exists in the network, end stations might receive duplicate messages. Switches might also learn end-station MAC addresses on multiple Layer 2 interfaces. These conditions result in an unstable network. Spanning-tree operation is transparent to end stations, which cannot detect whether they are connected to a single LAN segment or a switched LAN of multiple segments.
What is the bridge ID of a switch?
The IEEE 802.1D standard requires that each switch has an unique bridge identifier (bridge ID), which controls the selection of the root switch. Because each VLAN is considered as a different logical bridge with PVST+ and rapid PVST+, the same switch must have as many different bridge IDs as VLANs configured on it. Each VLAN on the switch has a unique 8-byte bridge ID. The two most-significant bytes are used for the switch priority, and the remaining six bytes are derived from the switch MAC address.