In the OSPF (Open Shortest Path First) protocol, each router calculates the shortest path to a network based on the information received from its directly connected neighbors.

OSPF configuration typically involves routers exchanging Link State Advertisements (LSAs) information only with other routers that are direct neighbors on the same local area network (LAN) or segmented wide area network (WAN). subnets.

Problems with Configuring Non-Directly Connected OSPF Neighbors

1. OSPF Area Violation: OSPF is designed to work with neighbors that are in the same area. Trying to establish an adjacency relationship with a router that is not in the same directly connected area can cause routing problems, since OSPF areas must be contiguous.
2. Adjacency Establishment Failure: OSPF uses a “Hello” process to establish and maintain adjacency relationships with other routers. This process depends on the routers being able to communicate directly with each other. If you try to configure an OSPF neighbor that is not directly connected, it is likely that “Hello” packets will not reach the other router, preventing the formation of an adjacency.
3. LSA Flood: Although it is technically possible to configure tunnels or VPNs to connect two OSPF routers that are not directly connected and try to establish an adjacency, this can lead to inefficient LSA flooding or inappropriate route distribution, since OSPF is not designed to handle these types of configurations natively.
4. Suboptimal Routes and Routing Loops: Configuring an OSPF neighbor that is not directly connected could lead to the creation of suboptimal routes and potentially routing loops, especially if the underlying network is not configured to properly handle these situations.

Solutions and Alternatives

• Use Static Routes or Transport Layer Routing Protocols: Instead of forcing an OSPF relationship with a non-directly connected router, you might consider using static routes (if administratively feasible) or using other routing protocols that are designed to handle connections over larger networks, such as BGP.
• VPN and OSPF over GRE: If you need to make two remote sites appear to be directly connected for OSPF, consider setting up a GRE tunnel over IPsec. OSPF can run over GRE and will treat the tunnel as a direct link, allowing LSAs to be propagated and adjacency maintained.

In summary, attempting to configure an OSPF neighbor that is not directly connected without additional measures such as tunnels is likely to lead to failures and unexpected behavior within a MikroTik or any other network that uses OSPF.

It is advisable to follow standard OSPF design practices to avoid these problems.