The port priority value is always paired with the port number to make up the 16-bit port identifier, which is used in various STP (Spanning Tree Protocol) operations and the STP state machines.
Unlike the 802.1D-1998 standard, the 802.1D-2004 standard uses only the four most significant bits for the port priority and it must be a multiple of 16. The new priority range available is 0 to 240 and is subject to the multiple of 16 restriction. The 802.1D-1998 standard uses the eight most significant bits for the port priority. The old priority range was 0 to 31 and was not subject to the multiple of 16 restriction.
To preserve backward compatibility and to use ExtremeXOS 11.5 or earlier configurations, the existing configure stpd ports priority command is available. If you have an ExtremeXOS 11.5 or earlier configuration, the switch interprets the port priority based on the 802.1D-1998 standard. If the switch reads a value that is not supported in ExtremeXOS 11.6 or later, the switch rejects the entry.
When you save the port priority value, the switch saves it as the command configure stpd ports port-priority with the corresponding change in value.
For example, if the switch reads the configure stpd ports priority 16 command from an ExtremeXOS 11.5 or earlier configuration, (which is equivalent to the command configure stpd ports priority 8 entered through CLI), the switch saves the value as configure stpd ports port-priority 128.
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