A shared link is an RSTP link that operates in half duplex. Its ports cannot use RSTP synchronization, so they transition like standard STP ports rather than rapidly reaching forwarding. section 15.3
Hub-connected switches
When SW1 and SW3 connect through a hub, the connection is half duplex and therefore becomes an RSTP shared link. The port may take 30 seconds to reach forwarding. section 15.3
Figure 15.7 RSTP differentiates between three link types: point-to-point, shared, and edge. A full-duplex link is considered a point-to-point link. A half-duplex link is considered a shared link. A link between a switch and an end host that uses PortFast is considered an edge link.
Use the diagram to compare shared links with full-duplex point-to-point links and PortFast edge links. section 15.3
Operational points:
- Half-duplex ports automatically use the shared link type. section 15.3
- Configure it manually with spanning-tree link-type shared in interface configuration mode when necessary. section 15.5
- Recognize Shr in show spanning-tree output as the shared-link type. section 15.3
