"Seriously?" Rathgar asked "You're bringing that into the dungeon?"
"Yes" Nimble replied curtly, his nose slightly upturned.
"Fine, but if it starts yapping, you have to deal with it."
"I will let you know this is a highly trained guard dog that will prove invaluable down in the dungeon."
"You even bought it armor? Where did you find a smith willing to do that??"
"I don't want him to get hurt. And anything can be had for the right price, you know that."
Dogs can be useful companions both in the dungeon and in the wilderness. They are loyal and watchful with far better ears and noses than humans, or even elves! But in a world with dangers such as dire rats, drakes, and rocs it's important to protect the ones you take into the dungeon.
Most forms of armor can be had for dogs, though the crafting of it can be difficult for many smiths to adjust to. If an armorer has made a particular type of armor for a dog before, than the cost for the armor is the standard price listed in the equipment section of the rule book. If the armorer has never made armor for a dog before, then the cost is 150% that listed in the rule book.
Magical forms of dog armor are very rare, but not unheard of. Common enchantments include Mirror Image, Detect Invisible, Locate Object, Resist Cold/Fire/Poison, and Protection from Evil.
To determine a dogs armor class while wearing armor, presume that they have a natural AC of 8, and a dex adjustment of +2.