Symptom

Cisco c9500 == [LACP + UDLD] == Juniper switch There are usually no UDLD errors despite Juniper not supporting UDLD protocol. One of these switches had no UDLD errors until adding a third/fourth link to the LACP connection.

Conditions

Sample condition: 17.9.4a and 17.9.5, running UDLD from Stackwise C9500 --multiple connections-- Juniper RE-QFX5120-48YM-8C

Workaround

Apply UDLD disable to ports on the LACP links.

Further Problem Description