This OID specifies which physical switch port(s) (1–65535) this rule applies to; only traffic entering or exiting these ports will be evaluated by the rule. A network engineer uses this to apply rules selectively—for example, enforcing stricter security on untrusted user ports while allowing administrative ports full access. For example, setting this to port 5 means the rule only affects traffic on physical port 5; traffic on other ports is unaffected.