The dog (개, gae) is read through loyalty and protection above everything else — of all the animals in this category, the dog is the one most consistently tied to a specific relationship (a trusted friend or family member) rather than an abstract fortune or warning.
A dog guarding your home calmly is read as genuine protection already in place — a trustworthy person or a stable situation looking out for you, whether or not you've consciously noticed it. A dog barking urgently or persistently is read as a warning worth taking seriously, since the dog's whole traditional role is alerting you to something before it becomes a real problem.
Being bitten by a dog carries a specifically personal sting compared to other animal-bite dreams on this site — because the dog is coded as a loyal, known figure rather than a wild or threatening one, being bitten is generally read as betrayal by someone trusted, a friend or close contact, rather than a stranger or an impersonal threat.
A lost dog finding its way home, or being reunited with a dog, is read warmly as reconciliation — a relationship repairing itself after a period of distance, one of the more emotionally direct readings in this whole category.