In an OSPF configuration, particularly on MikroTik routers that operate in multiple OSPF areas, the Router ID is unique for the entire OSPF process on the router, not per area. That is, even if your MikroTik router participates in multiple OSPF areas, it will use the same Router ID in all of them.

The Router ID is an IP address selected to uniquely identify the router within the OSPF network. OSPF uses this ID to identify the source routers of LSAs (Link State Advertisements) and to choose the Designated Router (DR) in multi-access networks. Router ID selection follows this hierarchy:

1. If a specific Router ID is manually configured for OSPF, that value will be used.
2. If a Router ID has not been configured manually, OSPF will automatically choose the Router ID based on the highest IP address of the loopback interfaces (if configured).
3. If there are no loopback interfaces configured, OSPF will use the highest IP address of the active interfaces at the time the OSPF process starts.

It is important to ensure that the Router ID is unique across the OSPF network to avoid routing conflicts. If two routers in the same OSPF network have the same Router ID, routing problems can arise due to confusion in route identification and adjacency formation.

When working with multiple OSPF areas on a MikroTik edge router, this principle remains: a single Router ID for the router's OSPF process, regardless of the number of areas it is connected to. This makes it easier to manage OSPF routing and ensures that the OSPF network topology is clear and consistent.