In ExtremeXOS 11.5 or earlier, Extreme Networks had two edge port implementations: edge port and edge port with safeguard.
The 802.1D-2004 standard has a bridge detection state machine, which introduced a third implementation of edge port behavior. The following list describes the behaviors of the different edge port implementations:
Edge port with safeguard prevents accidental or deliberate misconfigurations (loops) by having edge ports enter the blocking state upon receiving a BPDU. The 802.1D-2004 standard implements a bridge detection mechanism that causes an edge port to transition to a non-edge port upon receiving a BPDU; however, if the former edge port does not receive any subsequent BPDUs during a pre-determined interval, the port attempts to become an edge port.
If an 802.1D-2004 compliant safeguard port (edge port) connects to an 802.1D-1998 compliant edge port with safeguard configured, the old safeguard port enters the blocking state. Although the new safeguard port becomes a designated port, the link is not complete (and thus no loop is formed) because one side of the link is blocked.