Symptom

NGOAM loop-detection fails to block a loop after list of allowed vlans on a trunk is modified.

Conditions

* EVPN topology with NGOAM enabled * initially NGOAM correctly detects and blocks the loop on specific vlan (eg. 100) on problematic interface (Eth1/20) * user then modifies the allowed vlan list on Eth1/20, eg: switchport trunk allowed vlan add 200 * at this point loop is created in vlan 100 - ngoam still reports vlan 100 as blocked, however - stp state is instantiated for vlan 100 son Eth1/20

Workaround

* shut / no shut problematic interface

Further Problem Description