SSH Power Config: Connection Multiplexing & Keepalives

You already know a ~/.ssh/config Host alias. Now make SSH fast and resilient with two power-user defaults every heavy SSH user sets once and forgets.

1. Connection multiplexing — the first SSH connection opens a master; every later connection to the same host rides the SAME TCP/auth session over a control socket, so the second ssh/scp/git push is instant (no new handshake). You enable it with ControlMaster auto and a ControlPath socket, usually with ControlPersist so the master lingers.

2. Keepalives — ServerAliveInterval makes the client ping idle connections so they don't get silently dropped by NAT/firewalls.

Edit ~/.ssh/config so these apply to your hosts (a Host * block is the idiomatic place for defaults). Grading resolves your config with ssh -G labbox — the command that prints SSH's effective settings for a host — so the directives have to actually take effect, not just be present as text.

Required effective settings for labbox:

• ControlMaster = auto
• ControlPath = a real socket path (not none)
• ServerAliveInterval = a positive number (e.g. 30)