alt Hacker NewsYou do the standard thing: VPN into the datacenter's management network for IPMI-provided [0] KVMs for the isolated hosts, then connect to one or more of those KVMs.
If the software under test can attack the IPMI to gain access to the management network it's connected to, and then hop out to the Internet through either the VPN server or the IPMI client software, and the problem wasn't caused by a boneheaded misconfiguration, then that's a very interesting finding that everyone will want to hear... because that's a vulnerability in a component that's expected to safely run alongside hostile workloads.
[0] I'm using the name "IPMI", but the thing goes by many other names: BMC, LOM, iDRAC, iLO, etc, etc, etc. Whatever you call it, it's a little computer built into the motherboard to provide remote access and management to the system it's built into.
If you want to be even safer, you could use a physical network-connected KVM. The only interfaces those expose to the connected computer are HDMI (graphics read only) and USB peripherals (write only). Sometimes they can also physically power off the hosts to which they're connected.
It's a pretty darn slim surface for an attack. Technically doesn't meet the definition of an "air gap", but it gives you 100% of the utility of remote work with effectively 0% of the vulnerability, at the cost of a tiny amount of power and a few extra cables in the rack.