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SSH Connectivity Troubleshooting

When SSH fails, you need to separate “can I reach the host?” from “can I complete the handshake?” and then from “am I authorized?” This pillar focuses on the connectivity layer: ports, reachability, and common network-side blockers that cause SSH timeouts.

Related tools

  • Port Scanner — validate if port 22 (or custom) is reachable.
  • Config Generator — generate device configs and reduce manual mistakes.
  • Ping Monitor — confirm baseline reachability before SSH tests.

Connectivity-first checklist

  1. Can you reach the host? Start with Ping Monitor.
  2. Is the SSH port reachable? Use Port Scanner against port 22 (or the configured port).
  3. If the port is closed/filtered: check firewall rules, security groups, ACLs, and upstream policy.
  4. If the port is open but SSH still fails: suspect auth (keys), host key issues, or server-side config.

Common SSH symptoms

Ping works, SSH times out

Often a port-level block (ACL/firewall) or an SSH service not listening. Validate port reachability first.

Intermittent SSH drops

Look for unstable links, NAT timeouts, or MTU issues. Start with continuous ping/latency trends and trace the path.

Next steps

If SSH issues correlate with high latency or route shifts, pivot to Ping & Latency Diagnostics and Traceroute & Routing Analysis.