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Forum Discussion
RSTP Designated Root
Main switch GS752TP
G28 Fiber uplink to GS752TP (Switch B)
G26 Fiber uplink to GS724TP (Switch D)
Switch B
G25 fiber link to non-netgear switch (Switch C)
Switch C does not link to anything else
Switch D
G25 Fiber uplink to Main switch
Randomly the Main switch will disable port G26 and it doesn't resume normal until I reboot Main switch.
I noticed in STP settings that the designated root is the non-netgear switch (Switch C) and it is currently selected running smoothly. How does that switch get designated when it has no other path to the rest of the network?
I didn't notice what the designated root was when it disables G26 port on the main switch.
I found this entry on the "Switch D":
<182>1 2025-04-22T08:11:20.114-4:00Z 192.168.109.67-1 LLDP-6-NEIGHBOR_DEL proto_lldp.c(4308) %% Neighbor deleted on port GigabitEthernet25: Chassis ID 3C:37:86:CB:9A:AD, Port ID g26
<182>1 2025-04-22T08:11:19.454-4:00Z 192.168.109.67-1 STP-6-PORT_STATE proto_stp.c(820) %% Port GigabitEthernet25 moving from Forwarding to Disabled
<181>1 2025-04-22T08:11:19.444-4:00Z 192.168.109.67-1 TRAPMGR-5-STP_NEW_ROOT ksi_snmp.c(484) %% This bridge has changed to be the root bridge.
<181>1 2025-04-22T08:11:19.244-4:00Z 192.168.109.67-1 TRAPMGR-5-PORT_LINK_DOWN ksi_snmp.c(230) %% Interface GigabitEthernet25 link down
This is the entry on the main switch coinciding with the same time:
<182>1 2025-04-22T08:11:20.540-04:00 192.168.109.249-1 LLDP-6-NEIGHBOR_DEL proto_lldp.c(4321) %% Neighbor deleted on port GigabitEthernet26: Chassis ID 94:18:65:43:9C:CB, Port ID g25
<182>1 2025-04-22T08:11:19.790-04:00 192.168.109.249-1 STP-6-PORT_STATE proto_stp.c(820) %% Port GigabitEthernet26 moving from Forwarding to Disabled
<181>1 2025-04-22T08:11:19.550-04:00 192.168.109.249-1 TRAPMGR-5-PORT_LINK_DOWN ksi_snmp.c(230) %% Interface GigabitEthernet26 link down
The main switch should really be the designated root but i don't know how to configure that. I'm also guessing the non-netgear switch needs to have STP disabled on it.
Can someone help me understand what is happening? And what are the implications of a non-netgear switch with STP enabled?
2 Replies
Time to learn and understand RSTP (essentially the same for the basic STP)?
The Switch Bridge Priority must be carefully planned and set on every switch.
https://en.wikipedia.org/wiki/Spanning_Tree_Protocol#Rapid_Spanning_Tree_Protocol
Sometimes, I'd wish Netgear would publish such clear KB articles on RSTP configuration, as available with other vendors e.g. here Network Switch - Configure RSTP (Rapid-Spanning-Tree-Protocol) in a ring topology
appreciate the links for education. Question related more towards Netgear, when i have a switch that is non-netgear branded and it has RSTP enabled, does disabling the STP status on the Netgear port where this non-netgear switch is connected drop BPDU traffic so the other netgear switches essentially ignore the non-netgear switch?
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