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S4 and SecureStack RSTP Spanning Tree Question

S4 and SecureStack RSTP Spanning Tree Question

Rahman_Duran1
New Contributor III
Hi,

I have S4 as backbone and core of RSTP domain.

SYT_SRV_ROOM_S4_BACKBONE(su)->show spantree stats

Spanning tree status - enabled
Spanning tree instance - 0
Designated Root MacAddr - 00-1f-45-a0-9a-5e
Designated Root Priority - 4096
Designated Root Cost - 0
Designated Root Port - 0
Root Max Age - 20 sec
Root Hello Time - 2 sec
Root Forward Delay - 15 sec
Bridge ID MAC Address - 00-1f-45-a0-9a-5e
Bridge ID Priority - 4096
Bridge Max Age - 20 sec
Bridge Hello Time - 2 sec
Bridge Forward Delay - 15 sec
Topology Change Count - 1060
Time Since Top Change - 00 days 09:57:54
Max Hops

I just connected a B5 to S4 with two cables.
SYT-SRVROOM-DMZ-B5-2(su)->show spantree stats
Spanning tree status - enabled
Spanning tree instance - 0
Designated Root MacAddr - 00:1F:45:A0:9A:5E
Designated Root Port - ge.1.46
Designated Root Priority - 4096
Designated Root Cost - 20000
Root Max Age - 20
Root Hello Time - 2
Root Forward Delay - 15
Bridge ID MAC Address - 00:1F:45:91:9E:E8
Bridge ID Priority - 32768
Bridge Max Age - 20
Bridge Hello Time - 2
Bridge Forward Delay - 15
Topology Change Count - 477
Time Since Top Change - 1 days 4:36:36
Max Hops - 20

What I want to ask is if I look port status on B5, I see one port is blocking one port is forwarding as expected:
SYT-SRVROOM-DMZ-B5-2(su)->show spantree stats port ge.1.45-46
SID Port State Role Cost Priority
--- ---------- ---------------- ----------- -------- --------
0 ge.1.45 Discarding Alternate 20000 128
0 ge.1.46 Forwarding Root 20000 128

But if I look the ports on S4 that connected to B5, I see both of them forwarding:

SYT_SRV_ROOM_S4_BACKBONE(su)->show spantree stats port ge.2.35-36

SID Port State Role Cost Priority--- ---------- ---------------- ----------- -------- --------
0 ge.2.35 Forwarding Designated 20000 128
0 ge.2.36 Forwarding Designated 20000 128

Is this expected or something is wrong with my STP setup?

Thanks,

Rahman
5 REPLIES 5

Thanks for the quick answer 
GTM-P2G8KFN