Yes, you can definitely use the OSPF loopback address like the router-id or as a reference address in BGP when both protocols are running on a MikroTik device.

In fact, this is a common and recommended practice on networks that use both routing protocols for several key reasons:

1. Router-ID Stability

• OSPF and BGP They use a router identifier, known as router-id, which is crucial for the operations of the protocol. Using the loopback address ensures that the router-id do not change even if other interfaces go down, providing greater stability to the routing process.

2. Consistency between Protocols

• Use the same loopback address as router-id in both OSPF and BGP helps maintain consistency in routing configuration, which simplifies management and reduces the possibility of configuration errors.

3. Improved Peering Connectivity in BGP

• In BGP, especially in configurations where peering sessions are established with other autonomous systems, using the loopback address as the source address for BGP sessions can improve the reliability of peering connections. This is because loopback addresses are not directly affected by failures on physical interfaces, and dynamic routing can help achieve the loopback address even if some routes change.

Configuration in MikroTik RouterOS

To configure the loopback address and use it in both OSPF and BGP on a MikroTik RouterOS, you can follow these basic steps:

1. Set the Loopback Address:
   
   /interface bridge add name=loopback
/ip address add address=192.168.88.1/32 interface=loopback
   
2. Set Loopback Address as Router-ID in OSPF:
   
   /routing ospf instance set [ find default=yes ] router-id=192.168.88.1
   
3. Use the Loopback Address in BGP:
   • Set the loopback address as update-source in BGP peering configurations.
   
   /routing bgp peer set remote-address=192.168.89.2 update-source=loopback
   

Considerations

• Make sure the loopback address is well connected via OSPF routes to ensure other routers can reach it.
• Check firewall policies and route configurations to ensure that there are no restrictions that prevent OSPF and BGP connections from working properly using the loopback address.

Using a loopback address for OSPF and BGP in MikroTik is an effective technique to improve network stability and reliability, making it easier to manage complex routing configurations.