If you are running into issues with trunked LAG's using LACP between Cisco and Juniper, please try the following on the Cisco side...depending on the Cisco IOS and Model type:
yourswitch(config)# no vlan dot1q tag native
From Cisco's website: By default, the native VLAN traffic of a dot1q trunk is sent untagged, which cannot be double-tagged in the service provider network. Because of this situation, the native VLAN traffic might not be tunneled correctly. Be sure that the native VLAN traffic is always sent tagged in an asymmetrical link. To tag the native VLAN egress traffic and drop all untagged ingress traffic, enter the global vlan dot1q tag native command.
Remember to specify you native on both side's, as juniper's native = 0 / Cisco's native = 1
Good luck and let me know if you need a deep dive on any of these issues.
Cisco / Juniper Ceritifed in alot of stuff!
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