DR election uses criteria:
Priority: Higher wins. Default is . Priority means "never become DR."
Router ID: If priorities tie, highest Router ID wins.
The election is NOT preemptive. If a router with higher priority joins later, it doesn't take over as DR. The current DR keeps the role until it fails.
Router ID is chosen in this order:
- Manually configured router-id
- Highest IP on a loopback interface
- Highest IP on any active interface
Set loopback interfaces with stable IPs for predictable Router IDs. Don't leave it to chance.