STP States

Each port that belongs to a member VLAN participating in STP exists in one of the following states:

Blocking

A port in the blocking state does not accept ingress traffic, perform traffic forwarding, or learn MAC source addresses. The port receives STP BPDUs. During STP initialization, the switch always enters the blocking state.

Listening

A port in the listening state does not accept ingress traffic, perform traffic forwarding, or learn MAC source addresses. The port receives STP BPDUs. This is the first transitional state a port enters after being in the blocking state. The bridge listens for BPDUs from neighboring bridge(s) to determine whether the port should or should not be blocked.

Learning

A port in the learning state does not accept ingress traffic or perform traffic forwarding, but it begins to learn MAC source addresses. The port also receives and processes STP BPDUs. This is the second transitional state after listening. From learning, the port will change to either blocking or forwarding.

Forwarding

A port in the forwarding state accepts ingress traffic, learns new MAC source addresses, forwards traffic, and receives and processes STP BPDUs.

Disabled

A port in the disabled state does not participate in STP; however, it will forward traffic and learn new MAC source addresses.