Zorah
As a CCNP candidate and a CCNA, you may possibly be tempted to skip or just browse the numerous facts of Spanning Tree Protocol. After all, you learned all of that in your CCNA reports, right? That's appropriate, but it in no way hurts to review STP for a switching exam! Apart from, numerous of us feel of the 4 STP port states - but officially, there is a fifth one!
Disabled is not normally thought of as an STP port state, but Cisco does officially contemplate this to be an STP state. A disabled port is one that is administratively shut down.
As soon as the port is opened, the port will go into blocking state. As the name implies, the port can not do significantly in this state - no frame forwarding, no frame receiving, and for that reason no learning of MAC addresses. About the only thing this port can do is accept BPDUs from neighboring switches.
A port will then go from blocking mode into listening mode. The apparent question is "listening for what?" Listening for BPDUs - and this port can now send BPDUs as well. The port nonetheless can't forward or acquire information frames.
When the port goes from listening mode to learning mode, it really is finding prepared to send and obtain frames. In studying mode, the port starts to discover MAC addresses in preparation for adding them to its MAC address table.
Finally, a port can go into forwarding mode. This permits a port to forward and receive information frames, send and acquire BPDUs, and spot MAC addresses in its MAC table.
To see the STP mode of a offered interface, use the show spanning-tree interface command.
SW1#show spanning-tree interface quickly /11
Vlan Role Sts Expense Prio.Nbr Variety
---- --- --------- -------- ----------
VLAN0001 Desg FWD 19 128.11 P2p
To see these states in action, shut a port down in your CCNA / CCNP residence lab and continually run the show spanning interface command. When you see this in action on actual Cisco equipment, you are going to have no difficulty with BCMSN exam questions. Just do not practice this or any other Cisco command on a production network! the best
