At level 5, all rangers get the Extra Attack feature:
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
At level 3, the Hunter ranger archetype gets Hunter’s Prey, which lets them choose from 3 possible features. One option is Horde Breaker:
Once on each of your turns when you make a weapon attack, you can make another attack with the same weapon against a different creature that is within 5 feet of the original target and within range of your weapon.
At level 11, Hunters gain the Multiattack feature, which lets them choose between the Whirlwind Attack and Volley options. Whirlwind Attack says:
You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.
Am I right that Whirlwind Attack can not be used with Extra Attack, because you do not use the Attack action to make a Whirlwind Attack? Generally, can Extra Attack be used with any of the Hunter ranger’s special attacks?
I think with Horde Breaker, the “different creature” clause excludes any creature originally targeted with Whirlwind Attack. This means unless you have a reach weapon, Horde Breaker is useless with Whirlwind Attack. Am I mistaken?