Link-state change notifications (WS-C2960L)

[VinayPurohit7593]

Assume two nodes (computers) A & B connected to ports 1 and 2, respectively, of an a Catalyst switch. Both ports are part of the same VLAN. If computer B disconnects from port 2, can the switch be configured to send port-state notifications to all other ports (such as port 1) in that VLAN?  Will Spanning Tree BPDUs (Topology Change Notifications) provide this information? If not, are there standard in-band protocols (preferably at layer 2, and not layer 5 such as SNMP) supported by switches for querying the link status of specific ports?

[Martin L]

No, BPDU TCN (Topology Change Notifications) may inform others about topology change but not in details like who/where/what.  it does not carry any port-state info or notifications.  this BPDU TCN is to inform others to flush MACs in CAM tables.  you will need SNMP.

Notice "may" inform. Original STP (25 years old and no longer used) does sends BPDU TCN when end device port goes down if PortFast feature is not enabled.  This is somehow irrelevant now since either Portfast or Rapid STP is used/enabled.

What is this for ? what is your goal?

Regards, ML
**Please Rate All Helpful Responses **

[VinayPurohit7593]

Being able to detect the state of a particular port on a switch may allow an upstream node (such as a router that only works with virtual interfaces) to more quickly adapt to link failures. Going back to my original example, assume port 1 is a trunk VLAN (carrying VLANS 2, 3, 4), and ports 2, 3, and 4 are connected to separate WAN transport links and have default VLANs 2, 3, and 4, respectively. If the router at port 1 can detect a disconnect on port 2 (using a magical L2 mechanism that I seek through this thread), it can avoid usage of VLAN 2  and only use VLANs 3 and 4 until port 2 comes up again.