I am working on one issue with 4600 appliances in distributed and 13500 are cluster based setup.
When I tried to ping the IP-Address what is configured on disabled/disconnected interface were actually working. I am getting ICMP reply from the respective interface.
The surprising part is traffic was passing through an active interface. I confirmed, the IP is nowhere configured in my environment.
As per the sk41363 article, this is normal behavior due to weak ES (End System) model as described in RFC1122.
Note: I am managing those appliances in Gaia R77.30.
Please let me know Is it a normal behavior on Enterprise appliance and High-End appliance as well.