Rinaldi

As a CCNP candidate and a CCNA, you could be tempted to skip or just browse the a lot of details of Spanning Tree Protocol. Following all, you learned all of that in your CCNA scientific studies, right? That is appropriate, but it never hurts to evaluation STP for a switching exam! Apart from, numerous of us believe of the four STP port states - but officially, there's a fifth a single!

Disabled isn't normally thought of as an STP port state, but Cisco does officially contemplate this to be an STP state. A disabled port is a single that is administratively shut down.

When the port is opened, the port will go into blocking state. As the name implies, the port can not do a lot in this state - no frame forwarding, no frame receiving, and therefore no understanding of MAC addresses. About the only factor this port can do is accept BPDUs from neighboring switches.

A port will then go from blocking mode into listening mode. The obvious query is "listening for what?" Listening for BPDUs - and this port can now send BPDUs as effectively. The port nonetheless cannot forward or acquire data frames.

When the port goes from listening mode to understanding mode, it is acquiring prepared to send and obtain frames. In learning mode, the port begins to understand MAC addresses in preparation for adding them to its MAC address table.

Ultimately, a port can go into forwarding mode. This enables a port to forward and obtain information frames, send and receive 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 rapidly /11

goodman warranty registration

Vlan Role Sts Expense Prio.Nbr Sort

---

---- --- --------- -------- ----------

VLAN0001 Desg FWD 19 128.11 P2p

To see these states in action, shut a port down in your CCNA / CCNP house lab and continually run the show spanning interface command. When you see this in action on actual Cisco gear, you'll have no difficulty with BCMSN exam concerns. Just never practice this or any other Cisco command on a production network!