hi every body!
Does switch running rstp send bpdu every 2 seconds on its alternate port and back up port?
thanks a lot!
Tricky question that is in fact a very good follow up on the difference between a backup port and an alternate port.
If a bridge that has one or more alternate port loses its root port, it will not become root because it still hears from the root bridge from the alternate port(s).
If the only blocked ports are backup when the bridge loses its root port, then it will become root bridge. The port will stay backup port however, until new BPDUs are received on it, and it will not transmit any BPDU in the meantime.
No it does not. It could with MST (because the BPDU might carry some information for other instances, some of which having a designated role).
Only designated ports send BPDUs periodically.
There is also a feature called Bridge Assurance (I don't know how widely this is now available), that will cause all ports to send periodic BPDUs, but this is no standard behavior.
Do you see an alternate port sending periodic BPDUs?