auto: Use preference-based algorithm and assign preference based on position of device in the 'switches' list,
e.g., assuming a list of three switches, this would assign a preference of 200 to the first switch, 100 to the 2nd, and 0 to the third.
preference: Set preference for each switch manually using designated_forwarder_preferences key.
modulus: Use the default modulus-based algorithm.
If omitted, Port-Channels use the EOS default of modulus.
If omitted, Ethernet interfaces default to the 'auto' mechanism detailed above.
Path
NOTE: We are using the same format as jq to specify the path to the key.