I’ve noticed that Quagga is now deprecated and has been replaced by FRRouting (FRR), which is actively maintained.

Would it make sense to consider using FRRouting instead, or is Quagga preferred here for compatibility with the current infrastructure?

For example, FRRouting is used in SONiC, which suggests it is widely adopted in modern environments.

References :

https://en.wikipedia.org/wiki/FRRouting
https://news.ycombinator.com/item?id=20601039

I also came across OpenOSPFD, an OSPF routing daemon originally developed for OpenBSD, but it is marked as deprecated because it depends on an older CARP implementation.

Since our setup relies on the current CARP implementation, it would not be compatible in this context.

As a result, FRRouting appears to be a more up-to-date and appropriate option for us to use OSPF.

https://en.wikipedia.org/wiki/OpenOSPFD
https://www.freshports.org/net/openospfd/

FRRouting does not natively integrate with CARP, unlike OpenOSPFD which was designed to directly interact with it.

However, a similar behavior can be achieved by adjusting OSPF interface costs based on the CARP state.

An interface can be linked to a CARP virtual IP to know if the router is MASTER or BACKUP.

When the router is MASTER, it uses a normal cost, so it is preferred.

When it becomes BACKUP, a higher cost is applied, so other routers avoid it.

This way, OSPF follows the CARP failover and always sends traffic to the active router.

https://docs.opnsense.org/manual/dynamic_routing.html