The root switch is the switch with the highest speed ports.
Decisions on which port to block when two ports have equal cost depend on the port priority and identity.
All trunking ports are designated and not blocked.
Root switches have all ports set as root ports.
Non-root switches each have only one root port.
They are sent out by the root bridge only after the inferior BPDUs are sent.
They consist of a bridge priority and MAC address.
Only the root bridge will send out a BID.
They are used by the switches in a spanning tree topology to elect the root bridge.
The switch with the fastest processor will have the lowest BID.
To negotiate a trunk between switches
To set the duplex mode of a redundant link
to identify the shortest path to the root bridge
To prevent loops by sharing bridging tables between connected switches
To determine which ports will forward frames as part of the spanning tree
immediately loses its edge status
Inhibits the generation of a TCN
Goes immediately to a learning state
Becomes a normal spanning-tree port
Switch SW1 will block the broadcast and drop the frame.
Switch SW1 will forward the broadcast out all switch ports, except the originating port. This will generate an endless loop in the network.
Switch SW1 will forward the broadcast out all switch ports, except the originating port. All hosts in the network will replay with a unicast frame sent to host PC1.
Switch SW1 will forward the traffic out all switch ports except the originating port as a unicast frame. All hosts in the network will replay with a unicast frame sent to switch SW1.
PortFast is Cisco proprietary.
PortFast can negatively effect DHCP services.
PortFast is used to more quickly prevent and eliminate bridging loops.
Enabling PortFast on trunks that connect to other switches improves convergence.
If an access port is configured with PortFast, it immediately transitions from a blocking to a forwarding state.
Router_1 will drop the broadcast and reply with the MAC address of the next hop router.
Switch_A will reply with the MAC address of the Router_1 E0 interface.
Switch_A and Switch_B will continuously flood the message onto the network.
The message will cycle around the network until its TTL is exceeded.
Election of the root bridge
Blocking of the non-designated ports
Selection of the designated trunk port
Determination of the designated port for each segment
Configure all the interfaces on the switch as the static root ports.
Change the BPDU to a lower value than that of the other switches in the network.
Assign a lower IP address to the switch than that of the other switches in the network.
Set the switch priority to a smaller value than that of the other switches in the network.
Spanning tree blocks Gi 0/1 on S3.
Gi 0/2 on S3 transitions to a root port.
Port priority makes Gi 0/2 on S1 a root port.
S4 is already the root bridge, so there are no port changes.
The max-age timer
The spanning-tree hold down timer
The forward delay
the spanning-tree path cost
The blocking delay
RSTP uses a faster algorithm to determine root ports.
Both RSTP and STP use the portfast command to allow ports to immediately transition to forwarding state.
Like STP PortFast, an RSTP edge port that receives a BPDU loses its edge port status immediately and becomes a normal spanning-tree port.
Configuration commands to establish primary and secondary root bridges are identical for STP and RSTP.
Because of the format of the BPDU packet, RSTP is backward compatible with STP.
One root bridge per network
All non-designated ports forwarding
One root port per non-root bridge
Multiple designated ports per segment
One designated port per network
STP and RSTP use the same BPDU format.
STP specifies backup ports. RSTP has only root ports, alternate ports, and designated ports.
STP port states are independent of port roles. RSTP ties together the port state and port role.
STP waits for the network to converge before placing ports into forwarding state. RSTP places alternate ports into forwarding state immediately.
Two hosts communicating between ports Fa 0/2 and Fa 0/4 have a cost of 38.
The priority was statically configured to identify the root.
STP is disabled on this switch.
The timers have been altered to reduce convergence time.
number of ports
Base MAC address