Spanning tree Priority values
show spanning-tree interface gigabitethernet 0/2
Switch default
Instance Role State Cost Prio type
-------- ---- ----- ---- ---- ----
MST00 Designated Forwarding 20000 128.2 P2P
MST01 Designated Forwarding 20000 128.2 P2P
MST02 Designated Forwarding 20000 128.2 P2P
How the value 128.2 is calculated?
switching spanning-tree ieee-802.1s
edited Feb 22 at 9:54
Cown
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
add a comment |
show spanning-tree interface gigabitethernet 0/2
Switch default
Instance Role State Cost Prio type
-------- ---- ----- ---- ---- ----
MST00 Designated Forwarding 20000 128.2 P2P
MST01 Designated Forwarding 20000 128.2 P2P
MST02 Designated Forwarding 20000 128.2 P2P
How the value 128.2 is calculated?
switching spanning-tree ieee-802.1s
edited Feb 22 at 9:54
Cown
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
add a comment |
show spanning-tree interface gigabitethernet 0/2
Switch default
Instance Role State Cost Prio type
-------- ---- ----- ---- ---- ----
MST00 Designated Forwarding 20000 128.2 P2P
MST01 Designated Forwarding 20000 128.2 P2P
MST02 Designated Forwarding 20000 128.2 P2P
How the value 128.2 is calculated?
switching spanning-tree ieee-802.1s
edited Feb 22 at 9:54
Cown
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
show spanning-tree interface gigabitethernet 0/2
Switch default
Instance Role State Cost Prio type
-------- ---- ----- ---- ---- ----
MST00 Designated Forwarding 20000 128.2 P2P
MST01 Designated Forwarding 20000 128.2 P2P
MST02 Designated Forwarding 20000 128.2 P2P
How the value 128.2 is calculated?
switching spanning-tree ieee-802.1s
switching spanning-tree ieee-802.1s
edited Feb 22 at 9:54
Cown
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
edited Feb 22 at 9:54
Cown
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
edited Feb 22 at 9:54
Cown
6,30131030
edited Feb 22 at 9:54
Cown
6,30131030
edited Feb 22 at 9:54
Cown
6,30131030
6,30131030
asked Feb 22 at 9:42
kamakshikamakshi
111
asked Feb 22 at 9:42
kamakshikamakshi
111
asked Feb 22 at 9:42
kamakshikamakshi
111
111
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
128 is the default port priority (not cost) for xSTP interfaces, and .2 is the port number (eg: gi0/2).
In short, all things being equal (and in their default state), if two switches have multiple links joining them together, the lowest physical port number will generate the lowest port priority, and hence become the preferred root port.
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
Thanks for Info.
– kamakshi
Feb 22 at 10:17
add a comment |
128 is the default bridge priority. 2 is the port number and its default priority.
STP always chooses the bridge or port with the lowest number = highest priority. Paths to bridges with higher numbers are blocked. Put another way, the bridge with the overall lowest priority number is elected as root bridge. All ports leading to the root bridge are compared by their cost (lowest cost is chosen) and when there's a tie between bridges, the path to the bridge with the lowest priority number is chosen.
When there's a tie between ports (=two ports connecting to the same bridge) the ports' priorities are used.
Note that in both bridge and port priorities, the configured priority is prepended to the bridges MAC address or the port number. So, even with identical configured priorities there can never be a tie between bridges or ports as each hardware number is unique.
answered Feb 22 at 10:15
Zac67Zac67
30k21859
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
128 is the default port priority (not cost) for xSTP interfaces, and .2 is the port number (eg: gi0/2).
In short, all things being equal (and in their default state), if two switches have multiple links joining them together, the lowest physical port number will generate the lowest port priority, and hence become the preferred root port.
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
Thanks for Info.
– kamakshi
Feb 22 at 10:17
add a comment |
128 is the default port priority (not cost) for xSTP interfaces, and .2 is the port number (eg: gi0/2).
In short, all things being equal (and in their default state), if two switches have multiple links joining them together, the lowest physical port number will generate the lowest port priority, and hence become the preferred root port.
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
Thanks for Info.
– kamakshi
Feb 22 at 10:17
add a comment |
128 is the default port priority (not cost) for xSTP interfaces, and .2 is the port number (eg: gi0/2).
In short, all things being equal (and in their default state), if two switches have multiple links joining them together, the lowest physical port number will generate the lowest port priority, and hence become the preferred root port.
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
128 is the default port priority (not cost) for xSTP interfaces, and .2 is the port number (eg: gi0/2).
In short, all things being equal (and in their default state), if two switches have multiple links joining them together, the lowest physical port number will generate the lowest port priority, and hence become the preferred root port.
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
answered Feb 22 at 9:58
Benjamin DaleBenjamin Dale
7,0541036
7,0541036
Thanks for Info.
– kamakshi
Feb 22 at 10:17
add a comment |
Thanks for Info.
– kamakshi
Feb 22 at 10:17
Thanks for Info.
– kamakshi
Feb 22 at 10:17
Thanks for Info.
– kamakshi
Feb 22 at 10:17
add a comment |
128 is the default bridge priority. 2 is the port number and its default priority.
STP always chooses the bridge or port with the lowest number = highest priority. Paths to bridges with higher numbers are blocked. Put another way, the bridge with the overall lowest priority number is elected as root bridge. All ports leading to the root bridge are compared by their cost (lowest cost is chosen) and when there's a tie between bridges, the path to the bridge with the lowest priority number is chosen.
When there's a tie between ports (=two ports connecting to the same bridge) the ports' priorities are used.
Note that in both bridge and port priorities, the configured priority is prepended to the bridges MAC address or the port number. So, even with identical configured priorities there can never be a tie between bridges or ports as each hardware number is unique.
answered Feb 22 at 10:15
Zac67Zac67
30k21859
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
add a comment |
128 is the default bridge priority. 2 is the port number and its default priority.
STP always chooses the bridge or port with the lowest number = highest priority. Paths to bridges with higher numbers are blocked. Put another way, the bridge with the overall lowest priority number is elected as root bridge. All ports leading to the root bridge are compared by their cost (lowest cost is chosen) and when there's a tie between bridges, the path to the bridge with the lowest priority number is chosen.
When there's a tie between ports (=two ports connecting to the same bridge) the ports' priorities are used.
Note that in both bridge and port priorities, the configured priority is prepended to the bridges MAC address or the port number. So, even with identical configured priorities there can never be a tie between bridges or ports as each hardware number is unique.
answered Feb 22 at 10:15
Zac67Zac67
30k21859
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
add a comment |
128 is the default bridge priority. 2 is the port number and its default priority.
STP always chooses the bridge or port with the lowest number = highest priority. Paths to bridges with higher numbers are blocked. Put another way, the bridge with the overall lowest priority number is elected as root bridge. All ports leading to the root bridge are compared by their cost (lowest cost is chosen) and when there's a tie between bridges, the path to the bridge with the lowest priority number is chosen.
When there's a tie between ports (=two ports connecting to the same bridge) the ports' priorities are used.
Note that in both bridge and port priorities, the configured priority is prepended to the bridges MAC address or the port number. So, even with identical configured priorities there can never be a tie between bridges or ports as each hardware number is unique.
answered Feb 22 at 10:15
Zac67Zac67
30k21859
128 is the default bridge priority. 2 is the port number and its default priority.
STP always chooses the bridge or port with the lowest number = highest priority. Paths to bridges with higher numbers are blocked. Put another way, the bridge with the overall lowest priority number is elected as root bridge. All ports leading to the root bridge are compared by their cost (lowest cost is chosen) and when there's a tie between bridges, the path to the bridge with the lowest priority number is chosen.
When there's a tie between ports (=two ports connecting to the same bridge) the ports' priorities are used.
Note that in both bridge and port priorities, the configured priority is prepended to the bridges MAC address or the port number. So, even with identical configured priorities there can never be a tie between bridges or ports as each hardware number is unique.
answered Feb 22 at 10:15
Zac67Zac67
30k21859
answered Feb 22 at 10:15
Zac67Zac67
30k21859
answered Feb 22 at 10:15
Zac67Zac67
30k21859
answered Feb 22 at 10:15
Zac67Zac67
30k21859
30k21859
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
add a comment |
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
Is that 128 the default bridge priority or the default port priority? I thought bridge priorities are something like 32768 usually (by default) and go in steps of 4096 or something like that?
– ilkkachu
Feb 22 at 13:39
add a comment |
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