I am working with a customer with atleast 2 private data centers. They have no terminal servers providing console access to their networking gear (switches and routers and firewalls). They have built a network management sub-network on top of the underlying data network. They have shut down both data centers for several hours twice already and lose management access.
I am wrong in thinking this is a major problem? Shouldn't every data center have out of band access to their gear? I am thinking they should have a 4G LTE and/or analog line w modem into terminal servers (for example, Cisco routers with async network modules and octa cables into each devices console port).
Is there any other proper means of out of band management for networking gear than a terminal server with octa cable into each device?