diff --git a/annet/rulebook/nexus/vlandb.py b/annet/rulebook/nexus/vlandb.py
new file mode 100644
index 00000000..9aee7869
--- /dev/null
+++ b/annet/rulebook/nexus/vlandb.py
@@ -0,0 +1,172 @@
+import re
+from typing import Any, Dict, Iterator, Optional, Set, Tuple
+
+from annet.annlib.lib import cisco_collapse_vlandb as collapse_vlandb
+from annet.annlib.lib import cisco_expand_vlandb as expand_vlandb
+from annet.annlib.types import Op
+
+
+# Constants
+NEXUS_SWITCHPORT_VLAN_CHUNK: int = 64
+NEXUS_DEFAULT_RANGE: range = range(1, 4095)  # 4094 inclusive
+
+
+def swtrunk(rule: Dict[str, Any], key: Tuple, diff: Dict[str, Any], **_) -> Iterator[Tuple[bool, str, Optional[list]]]:
+    """
+    Patch logic for Cisco Nexus `switchport trunk allowed vlan` command.
+    Processes VLAN configuration changes and yields commands to apply.
+    """
+    yield from _process_vlandb(rule, key, diff, NEXUS_SWITCHPORT_VLAN_CHUNK)
+
+
+def _process_vlandb(
+    rule: Dict[str, Any], key: Tuple, diff: Dict[str, Any], chunk_size: int
+) -> Iterator[Tuple[bool, str, Optional[list]]]:
+    """
+    Core logic for processing VLAN database changes.
+
+    Args:
+        rule: Configuration rule dictionary
+        key: Rule identifier tuple
+        diff: Dictionary containing ADDED, REMOVED, and AFFECTED operations
+        chunk_size: Maximum number of VLAN ranges per command
+
+    Yields:
+        Tuples of (should_add: bool, command: str, children: Optional[list])
+    """
+    # Early exit if no changes
+    if not diff[Op.ADDED] and not diff[Op.REMOVED]:
+        return
+
+    # Process affected blocks with modified content
+    for affected in diff[Op.AFFECTED]:
+        yield (True, affected["row"], affected["children"])
+
+    # Parse added and removed VLAN configurations
+    pref_added, vlans_new, new_blocks = _parse_vlancfg_actions(diff[Op.ADDED])
+    pref_removed, vlans_old, old_blocks = _parse_vlancfg_actions(diff[Op.REMOVED])
+
+    # Handle case where no existing configuration exists
+    if not diff[Op.REMOVED]:
+        vlans_old = set(NEXUS_DEFAULT_RANGE)
+
+    # Use removed prefix if added prefix is not available
+    if not pref_added:
+        pref_added = pref_removed
+
+    # Handle "none" configuration special case
+    if len(diff[Op.ADDED]) == 1 and not vlans_new:
+        yield (True, f"{pref_added} none", None)
+        return
+
+    # Process blocks where VLAN remains but content changed
+    removed_blocks_keys = set(old_blocks.keys()) - set(new_blocks.keys())
+    for vlan_id in removed_blocks_keys & vlans_new:
+        yield (True, f"{pref_added} {vlan_id}", old_blocks[vlan_id])
+
+    # Calculate VLANs to add and remove
+    vlans_to_remove = vlans_old - vlans_new
+    vlans_to_add = vlans_new - vlans_old
+
+    # Generate remove commands in chunks
+    if vlans_to_remove:
+        collapsed_remove = collapse_vlandb(vlans_to_remove)
+        for chunk in _chunked(collapsed_remove, chunk_size):
+            yield (False, f"{pref_added} remove {','.join(chunk)}", None)
+
+    # Generate add commands in chunks
+    if vlans_to_add:
+        collapsed_add = collapse_vlandb(vlans_to_add)
+        for chunk in _chunked(collapsed_add, chunk_size):
+            yield (True, f"{pref_added} add {','.join(chunk)}", None)
+
+    # Process new VLAN blocks
+    for vlan_id, block in new_blocks.items():
+        yield (True, f"{pref_added} {vlan_id}", block)
+
+
+def _chunked(items: list, chunk_size: int) -> Iterator[list[str]]:
+    """
+    Split a list into chunks of specified size.
+
+    Args:
+        items: List to split
+        chunk_size: Maximum size of each chunk
+
+    Yields:
+        Chunks of the original list
+    """
+    for i in range(0, len(items), chunk_size):
+        yield items[i : i + chunk_size]
+
+
+def _parse_vlancfg_actions(
+    actions: list[Dict[str, Any]],
+) -> Tuple[Optional[str], Set[int], Dict[str, Any]]:
+    """
+    Parse VLAN configuration actions to extract prefix, VLAN IDs, and blocks.
+
+    Args:
+        actions: List of action dictionaries with 'row' and 'children' keys
+
+    Returns:
+        Tuple of (prefix, vlan_ids, blocks)
+    """
+    prefix: Optional[str] = None
+    vlan_ids: Set[int] = set()
+    blocks: Dict[str, Any] = {}
+
+    for action in actions:
+        current_prefix, vlan_set = _parse_vlancfg(action["row"])
+
+        # Use the first encountered prefix
+        if prefix is None:
+            prefix = current_prefix
+
+        # Handle VLAN blocks with children
+        if action["children"]:
+            if len(vlan_set) != 1:
+                raise ValueError(f"VLAN block must contain exactly one VLAN ID: {action['row']}")
+            vlan_id = next(iter(vlan_set))
+            blocks[str(vlan_id)] = action["children"]
+
+        vlan_ids.update(vlan_set)
+
+    return prefix, vlan_ids, blocks
+
+
+def _parse_vlancfg(row: str) -> Tuple[str, Set[int]]:
+    """
+    Parse VLAN configuration string into prefix and VLAN IDs.
+
+    Args:
+        row: Configuration string (e.g., "switchport trunk allowed vlan 1-10,20")
+
+    Returns:
+        Tuple of (command_prefix, set_of_vlan_ids)
+
+    Raises:
+        ValueError: If the row cannot be parsed
+    """
+    # Normalize spaces around commas
+    normalized_row = re.sub(r",\s+", ",", row)
+    words = normalized_row.split()
+
+    # Handle "none" configuration
+    if words[-1] == "none":
+        prefix = " ".join(words[:-1])
+        return prefix, set()
+
+    # Validate VLAN configuration format
+    if not re.match(r"[\d,-]+$", words[-1]):
+        raise ValueError(f"Unable to parse VLAN configuration row: {row}")
+
+    # Extract prefix and VLAN configuration
+    prefix_words = words[:-2] if words[-2] == "add" else words[:-1]
+    prefix = " ".join(prefix_words)
+    vlan_config = words[-1]
+
+    # Expand VLAN ranges to individual IDs
+    vlan_ids = expand_vlandb(vlan_config)
+
+    return prefix, vlan_ids