diff --git a/napalm_opnsense/opnsense.py b/napalm_opnsense/opnsense.py
index 24cc66c..4009791 100644
--- a/napalm_opnsense/opnsense.py
+++ b/napalm_opnsense/opnsense.py
@@ -298,7 +298,11 @@ class OPNsenseDriver(FirewallDriver):
                 "gateway": "192.168.1.1",
                 "family": "ipv4",
                 "prefix_length": 24,
+                "vlan_id": 20,
             }
+
+        ``vlan_id`` is ``None`` for interfaces that are not 802.1Q VLAN
+        sub-interfaces (e.g. the untagged management/LAN interface).
         """
         import ipaddress
 
@@ -307,7 +311,7 @@ class OPNsenseDriver(FirewallDriver):
 
         networks: List[Dict[str, Any]] = []
 
-        def _add(ifname: str, cidr: str, family: str) -> None:
+        def _add(ifname: str, cidr: str, family: str, vlan_id: int | None) -> None:
             """Parse a CIDR string (e.g. '10.0.0.1/24') and append to networks."""
             try:
                 iface_obj = ipaddress.ip_interface(cidr)
@@ -320,6 +324,7 @@ class OPNsenseDriver(FirewallDriver):
                     "gateway": str(iface_obj.ip),
                     "family": family,
                     "prefix_length": net.prefixlen,
+                    "vlan_id": vlan_id,
                 })
             except ValueError:
                 pass
@@ -329,13 +334,21 @@ class OPNsenseDriver(FirewallDriver):
             if not name:
                 continue
 
+            vlan_id: int | None = None
+            raw_tag = iface.get("vlan_tag")
+            if raw_tag:
+                try:
+                    vlan_id = int(raw_tag)
+                except (TypeError, ValueError):
+                    vlan_id = None
+
             # Primary format: flat CIDR strings in addr4/addr6
             addr4: str = iface.get("addr4", "")
             addr6: str = iface.get("addr6", "")
             if addr4:
-                _add(name, addr4, "ipv4")
+                _add(name, addr4, "ipv4", vlan_id)
             if addr6:
-                _add(name, addr6, "ipv6")
+                _add(name, addr6, "ipv6", vlan_id)
 
             # Fallback: ipv4/ipv6 arrays where ipaddr may include prefix
             if not addr4:
@@ -344,14 +357,14 @@ class OPNsenseDriver(FirewallDriver):
                     subnet = entry.get("subnetbits") or entry.get("prefix_length")
                     cidr = f"{ip_field}/{subnet}" if subnet and "/" not in ip_field else ip_field
                     if cidr:
-                        _add(name, cidr, "ipv4")
+                        _add(name, cidr, "ipv4", vlan_id)
             if not addr6:
                 for entry in iface.get("ipv6") or []:
                     ip_field = entry.get("ipaddr") or entry.get("ip", "")
                     prefix = entry.get("prefixlen") or entry.get("prefix_length")
                     cidr = f"{ip_field}/{prefix}" if prefix and "/" not in ip_field else ip_field
                     if cidr:
-                        _add(name, cidr, "ipv6")
+                        _add(name, cidr, "ipv6", vlan_id)
 
         return networks