BGP - using private ASNs with private IPs

What is the benefit of using BGP with a private ASN and private IPv4 or IPv6 addresses if you have no public addresses to advertise? Well, there are still some advantages to deploying such an arrangement, and these are listed below:

1. Even with a private ASN used for the autonomous system, an enterprise can still achieve multi-homing to multiple ISPs for redundancy and failover. BGP can be used to manage the failover process for outgoing traffic.
2. BGP may be used internally by the enterprise for implementations of MPLS VPNs, or traffic engineering, and in such cases, BGP and private ASNs are still necessary.
3. Complex network topologies often require BGP even if you’re not advertising to the Internet at large. This may be needed for extensively large networks, or in order to manage IP address spaces more efficiently.

So there are reasons to employ BGP and private ASNs even if you’re not advertising public addresses that you may own.

It is also possible to use public IPs with private ASes.

Links

https://networklessons.com/bgp/singledual-homed-and-multi-homed-designs