2. Consider this switched network (from CNA Scaling Networks 2.1.2.8). Please ig
ID: 3714913 • Letter: 2
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2. Consider this switched network (from CNA Scaling Networks 2.1.2.8). Please ignore the boxes drawn on top of each inter-switch link. Assume that Spanning Tree Protocol (STP) is running on this network. The table below shows the Bridge ID (BID) value for each switch, split into Priority and MAC Address parts. All ports are on VLAN 1 G1/1 S1 S2 Fa0/1 G1 G1/3 G1/1 Fa0/1 S3 S4 Priority 32769 24577 32769 32769 MAC Address S1 S2 S3 S4 000A00222222 000A00333333 000A00444444 (5 points) When STP protocol is run, which switch (S1, S2, S3 or S4) will become the Root Switch for this network? Why? a.Explanation / Answer
A)
In a default Spanning Tree Protocol (STP) configuration network, a Switch with the lowest MAC address will be elected as the Root Bridge (Root Switch)
It quite easy. You do not need to convert hex into decimal. Just compare figures from left to right and find out which one get higher number as a first one.
Your example 003 and 000,
first figure digit 0 and 0,
second: 0 and 0,
third: 3 and 0, 3 is higher then 0, the second MAC is the lower address.
B)
(i) designated port
(ii)designated port
(iii)root port
(iii)root port
(iv)root port
others are alternative ports
explanation:
C)S4
The Switch Ports will go into a blocking state at the time of election process, when a switch receives a BPDU on a port that indicates a better path to the Root Switch (Root Bridge), and if a port is not a Root Port or a Designated Port.
A port in the blocking state does not participate in frame forwarding and also discards frames received from the attached network segment. During blocking state, the port is only listening to and processing BPDUs on its interfaces. After 20 seconds, the switch port changes from the blocking state to the listening state
MAC Address:00A00111111(lowest mac Address)In a default Spanning Tree Protocol (STP) configuration network, a Switch with the lowest MAC address will be elected as the Root Bridge (Root Switch)
It quite easy. You do not need to convert hex into decimal. Just compare figures from left to right and find out which one get higher number as a first one.
Your example 003 and 000,
first figure digit 0 and 0,
second: 0 and 0,
third: 3 and 0, 3 is higher then 0, the second MAC is the lower address.
B)
(i) designated port
(ii)designated port
(iii)root port
(iii)root port
(iv)root port
others are alternative ports
explanation:
- Root ports - exist on non- root bridges and are switch ports with best cost path to root bridge.
- Designated ports - exist on root and non-root bridges. For root bridge all ports are designated ports!!! (quick examination but there can be confusion if root-bridge role is distributed among VLANs or when there is default VLAN root bridge selected with other mechanism as other VLANs). Please keep in mind that on segment is allowed only one designated port!!!. Designate ports also as root ports are capable populate mac-address-table (CAM table of switch)
C)S4
The Switch Ports will go into a blocking state at the time of election process, when a switch receives a BPDU on a port that indicates a better path to the Root Switch (Root Bridge), and if a port is not a Root Port or a Designated Port.
A port in the blocking state does not participate in frame forwarding and also discards frames received from the attached network segment. During blocking state, the port is only listening to and processing BPDUs on its interfaces. After 20 seconds, the switch port changes from the blocking state to the listening state
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