# UNDF: UNDF-2026-000000183
--- a/neutron/agent/linux/iptables_firewall.py
+++ b/neutron/agent/linux/iptables_firewall.py
@@ -73,7 +73,7 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
         self.unfiltered_ports = {}
-        self.trusted_ports = []
+        self.trusted_ports = set()
         self.ipconntrack = ip_conntrack.get_conntrack(
             self.iptables.get_rules_for_table, self.filtered_ports,
             self.unfiltered_ports, namespace=namespace,
@@ -151,7 +151,7 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
     def process_trusted_ports(self, port_ids):
         """Process ports that are trusted and shouldn't be filtered."""
         for port in port_ids:
             if port not in self.trusted_ports:
                 jump_rule = self._generate_trusted_port_rules(port)
                 self._add_rules_to_chain_v4v6(
                     'FORWARD', jump_rule, jump_rule, comment=ic.TRUSTED_ACCEPT)
                 self._add_nat_short_ciruit(port)
-                self.trusted_ports.append(port)
+                self.trusted_ports.add(port)

     def remove_trusted_ports(self, port_ids):
         for port in port_ids:
             if port in self.trusted_ports:
                 jump_rule = self._generate_trusted_port_rules(port)
                 self._remove_rule_from_chain_v4v6(
                     'FORWARD', jump_rule, jump_rule)
                 self._remove_nat_short_ciruit(port)
-                self.trusted_ports.remove(port)
+                self.trusted_ports.discard(port)