Add mlag_on_orphan_port_channel_downlink knob to turn on the new beha…

…vior

ansible_collections/arista/avd/molecule/eos_designs_unit_tests/intended/configs/UNDERLAY-MULTICAST-L3LEAF1A.cfg

@@ -37,6 +37,7 @@ interface Port-Channel6
    switchport
    switchport trunk allowed vlan none
    switchport mode trunk
+   mlag 6
 !
 interface Ethernet1
    description P2P_LINK_TO_UNDERLAY-MULTICAST-SPINE1_Ethernet1

ansible_collections/arista/avd/molecule/eos_designs_unit_tests/intended/structured_configs/UNDERLAY-MULTICAST-L3LEAF1A.yml

@@ -143,6 +143,7 @@ port_channel_interfaces:
   shutdown: false
   mode: trunk
   vlans: none
+  mlag: 6
 ethernet_interfaces:
 - name: Ethernet3
   peer: UNDERLAY-MULTICAST-L3LEAF1B

ansible_collections/arista/avd/molecule/eos_designs_unit_tests/inventory/group_vars/SINGLE_LINK_TO_MLAG_PAIR.yml

@@ -4,6 +4,10 @@ fabric_name: SINGLE_LINK_TO_MLAG_PAIR
 design:
   type: l2ls
 
+type: leaf
+
+mlag_on_orphan_port_channel_downlink: false
+
 leaf:
   defaults:
     mlag_peer_ipv4_pool: 10.10.255.0/24

ansible_collections/arista/avd/molecule/eos_designs_unit_tests/inventory/hosts.yml

@@ -285,29 +285,44 @@ all:
         WAN_TESTS:
           children:
             AUTOVPN_TESTS:
+              children:
+                AUTOVPN_RRS:
+                  hosts:
+                    autovpn-rr1:
+                    autovpn-rr2:
               hosts:
                 autovpn-edge:
-                autovpn-rr1:
-                autovpn-rr2:
             CV_PATHFINDER_TESTS:
               hosts:
                 cv-pathfinder-edge:
+                cv-pathfinder-edge-no-common-path-group:
                 cv-pathfinder-transit:
-                cv-pathfinder-pathfinder:
               children:
-                CV_PATHFINDER_MULTI_RR_TESTS:
+                CV_PATHFINDERS:
                   hosts:
-                    cv-pathfinder-pathfinder1:
-                    cv-pathfinder-pathfinder2:
+                    cv-pathfinder-pathfinder:
+                  children:
+                    CV_PATHFINDER_MULTI_RR_TESTS:
+                      hosts:
+                        cv-pathfinder-pathfinder1:
+                        cv-pathfinder-pathfinder2:
+        UPLINK_P2P_VRFS_TESTS:
+          hosts:
+            UPLINK_P2P_VRFS_TESTS_SPINE1:
+            UPLINK_P2P_VRFS_TESTS_SPINE2:
+            UPLINK_P2P_VRFS_TESTS_LEAF1:
+            UPLINK_P2P_VRFS_TESTS_L2LEAF1:
+        NEW_NETWORK_SERVICES_BGP_VRF_CONFIG_TESTS:
+          hosts:
+            new_network_services_bgp_vrf_config_true:
+            new_network_services_bgp_vrf_config_false:
         SINGLE_LINK_TO_MLAG_PAIR:
-          children:
-            L2LS_LEAFS:
-              hosts:
-                SL-LEAF0A:
-                SL-LEAF0B:
-                SL-LEAF1A:
-                SL-LEAF1B:
-                SL-MLEAF1:
+          hosts:
+            SL-LEAF0A:
+            SL-LEAF0B:
+            SL-LEAF1A:
+            SL-LEAF1B:
+            SL-MLEAF1:
         AVD_LAB:
           children:
             DC1_FABRIC:

ansible_collections/arista/avd/plugins/plugin_utils/eos_designs_facts/uplinks.py

@@ -286,13 +286,13 @@ def _get_port_channel_uplink(self: EosDesignsFacts, uplink_index: int, uplink_in
             # Override our description on port-channel to be peer's group name if they are mlag pair or A/A #}
             uplink["channel_description"] = uplink_switch_facts.shared_utils.group
 
-        # Used to determine whether or not port-channel towards uplink switch should have an mlag id
+        # Used to determine whether or not port-channel should have an mlag id configure on the uplink_switch
         unique_uplink_switches = set(self.shared_utils.uplink_switches)
         if self.shared_utils.mlag is True:
             # Override the peer's description on port-channel to be our group name if we are mlag pair #}
             uplink["peer_channel_description"] = self.shared_utils.group
 
-            # Updating unique_uplink_switches with this switch's mlag peer's uplink switches
+            # Updating unique_uplink_switches with our mlag peer's uplink switches
             unique_uplink_switches.update(self.shared_utils.mlag_peer_facts.shared_utils.uplink_switches)
 
         # Only enable mlag for this port-channel on the uplink switch if there are multiple unique uplink switches

ansible_collections/arista/avd/roles/eos_designs/docs/tables/fabric-settings.md

@@ -8,6 +8,7 @@
     | Variable | Type | Required | Default | Value Restrictions | Description |
     | -------- | ---- | -------- | ------- | ------------------ | ----------- |
     | [<samp>enable_trunk_groups</samp>](## "enable_trunk_groups") | Boolean |  | `False` |  | Enable Trunk Group support across eos_designs.<br>Warning: Because of the nature of the EOS Trunk Group feature, enabling this is "all or nothing".<br>*All* vlans and *all* trunks towards connected endpoints must be using trunk groups as well.<br>If trunk groups are not assigned to a trunk, no vlans will be enabled on that trunk.<br>See "Details on enable_trunk_groups" below before enabling this feature.<br> |
+    | [<samp>mlag_on_orphan_port_channel_downlink</samp>](## "mlag_on_orphan_port_channel_downlink") | Boolean |  | `True` |  | If `true` (default) an MLAG ID will always be configured on a Port-Channel Downlink even if the downlink is only on one MLAG switch.<br>If `false` an MLAG ID will only be configured on Port-Channel Downlinks dual-homed to two MLAG switches.<br>Note the default value will change to `false` in AVD version 5.0 |
     | [<samp>only_local_vlan_trunk_groups</samp>](## "only_local_vlan_trunk_groups") | Boolean |  | `False` |  | A vlan can have many trunk_groups assigned.<br>To avoid unneeded configuration changes on all leaf switches when a new trunk group is added,<br>this feature will only configure the vlan trunk groups matched with local connected_endpoints.<br>See "Details on only_local_vlan_trunk_groups" below.<br>Requires "enable_trunk_groups: true".<br> |
     | [<samp>p2p_uplinks_mtu</samp>](## "p2p_uplinks_mtu") | Integer |  | `9214` | Min: 68<br>Max: 65535 | Point to Point Links MTU. |
     | [<samp>p2p_uplinks_qos_profile</samp>](## "p2p_uplinks_qos_profile") | String |  |  |  | QOS Profile assigned on all infrastructure links. |
@@ -49,6 +50,11 @@
     # See "Details on enable_trunk_groups" below before enabling this feature.
     enable_trunk_groups: <bool; default=False>
 
+    # If `true` (default) an MLAG ID will always be configured on a Port-Channel Downlink even if the downlink is only on one MLAG switch.
+    # If `false` an MLAG ID will only be configured on Port-Channel Downlinks dual-homed to two MLAG switches.
+    # Note the default value will change to `false` in AVD version 5.0
+    mlag_on_orphan_port_channel_downlink: <bool; default=True>
+
     # A vlan can have many trunk_groups assigned.
     # To avoid unneeded configuration changes on all leaf switches when a new trunk group is added,
     # this feature will only configure the vlan trunk groups matched with local connected_endpoints.

ansible_collections/arista/avd/roles/eos_designs/python_modules/underlay/port_channel_interfaces.py

@@ -63,7 +63,8 @@ def port_channel_interfaces(self) -> list | None:
             elif (vlans := link.get("vlans")) is not None:
                 port_channel_interface["vlans"] = vlans
 
-            if self.shared_utils.mlag is True and link.get("mlag", True):
+            # Configure MLAG on MLAG switches unless "mlag_on_orphan_port_channel_downlink" is False AND link.mlag is False
+            if self.shared_utils.mlag is True and (get(self._hostvars, "mlag_on_orphan_port_channel_downlink", default=True) or link.get("mlag", True)):
                 port_channel_interface["mlag"] = int(link.get("channel_group_id"))
 
             if (short_esi := link.get("short_esi")) is not None:

ansible_collections/arista/avd/roles/eos_designs/python_modules/underlay/utils.py

@@ -11,7 +11,6 @@
 from ansible_collections.arista.avd.plugins.plugin_utils.utils import get
 
 
-
 class UtilsMixin:
     """
     Mixin Class with internal functions.
@@ -97,7 +96,6 @@ def _underlay_links(self) -> list:
                             }
                             for subinterface in subinterfaces
                         ]
-
                     underlay_links.append(strip_empties_from_dict(link))
 
         return natural_sort(underlay_links, "interface")

ansible_collections/arista/avd/roles/eos_designs/schemas/schema_fragments/mlag_on_orphan_port_channel_downlink.schema.yml

@@ -0,0 +1,18 @@
+# Copyright (c) 2024 Arista Networks, Inc.
+# Use of this source code is governed by the Apache License 2.0
+# that can be found in the LICENSE file.
+# yaml-language-server: $schema=../../../../plugins/plugin_utils/schema/avd_meta_schema.json
+# Line above is used by RedHat's YAML Schema vscode extension
+# Use Ctrl + Space to get suggestions for every field. Autocomplete will pop up after typing 2 letters.
+type: dict
+keys:
+  mlag_on_orphan_port_channel_downlink:
+    type: bool
+    documentation_options:
+      table: fabric-settings
+    description: |-
+      If `true` (default) an MLAG ID will always be configured on a Port-Channel Downlink even if the downlink is only on one MLAG switch.
+      If `false` an MLAG ID will only be configured on Port-Channel Downlinks dual-homed to two MLAG switches.
+      Note the default value will change to `false` in AVD version 5.0
+    # TODO: AVD5.0 change default to false and remove the note from the description.
+    default: true