I disagree, Out of Band Network Management (OOBM) is extremely trivial to implement. Most companies however don't see the value of OOBM until they have a major fault. The setup costs can be high, and the ongoing operational costs of OOBM infrastructure and links is also significant.
I've built dozens of OOBM networks using fibre and 4G with the likes of Opengear. In instances, often deploying OOBM ahead of infrastructure rollouts so hardware can be delivered to site directly from factory, rather than go through a staging environment which adds time, cost and complexity.
OOB for carriers is significantly more complex; especially when you may be the only realistic access option in certain locations. However, given the rise of Starlink I think it becomes closer to "trivial" when the math becomes $100/mo/location + some minimal always-on OOB infrastructure on prem + cloud. Even in heavy-monopoly situations, you can usually guarantee the Starlink to Internet path due to the traffic bypassing the transport carriers on the ground (bent pipe to LEO sat) and landing at IXPs/near telco houses which egress direct to transit carriers.
We have a major incident wherein our firewall was totally down last month. The director at the end suggested that we need to have RS232 cable for out of band communication for such eventualities in the future.
Makes one realize the reliability of RS232 in today’s day and age.
