This read-create value defines the set of switch ports that belong to a given VLAN protection group, i.e. the ports eligible to carry the protected VLAN's traffic and participate in its failover scheme. Administrators populate it when building a protect group so the switch knows exactly which physical ports to switch traffic between if one path fails. A typical portlist might encode ports 1 and 2 as the pair of uplinks the group can fail over between.