Here's a video Paint Rock 00 posted in the Al dogs section recently. I didn't add the negative consequence like they did in this video, I'll probably implement that one day.
I was out in Bankhead and saw a rat snake sunning on a rock. My dog chased it initially, but I was able to call him off before he got to it. I then got out of sight of the snake, and then turned around to pass it again a few times. Whenever he focused on it, I would correct his behavior. He hasn't gone after a snake since, and I've seen dozens, and he's probably smelled hundreds. My dog is very eager to please, so I doubt it would be this easy for other dogs.
I think another thing that helps has been taking him squirrel hunting. He's becoming more focused on them as he matures. A mouthful of warm twitching squirrel is pure bliss for him.
I don't kill snakes when he's with me. I figured that would give him motivation to sniff them out.
I would never trust any dog 100% to not chase a snake. They are domesticated wolves.
Disclaimer: I'm no dog training expert, that's just what I did.
