Do spawners work in The Nether (top of nether)—especially Skeleton, Cave Spider, Zombie Pigman, and Zombie spawners?
All spawners that normally work will work, so long as the conditions are met. For example, most animals need nearby grass, most hostiles need darkness, and all mobs need enough space to spawn.
Here is an image of zombies spawning in the nether from a spawner, which the other answer claims to be impossible:
Only Mobs which can actually spawn on netherrack/brick will spawn. That means, skeleton, blaze, and zombie pigmen will spawn, but zombies and cave spiders wont.
The only mobs which can naturally spawn the nether are:
- Zombie Pigmen
Edit: The Nether still allows every kind of mob if you place the spawner on the correct block. For example, endermen will spawn if you place the block on endstone.