SSH Connectivity Problems
SSH failures are often blamed on credentials, but the majority of issues are caused by networking, routing, or port-level filtering.
Common SSH Failure Symptoms
- Connection timeout
- Connection refused
- Session freezes after login
- Intermittent disconnects
- SSH works locally but not remotely
Primary Causes
- Closed or filtered TCP port 22
- Firewall or security group rules
- NAT or asymmetric routing
- Packet loss affecting TCP sessions
- ISP port blocking
How to Diagnose SSH Issues
Port Scanner
Verify whether the SSH port is open, filtered, or closed from your current network perspective.
Ping Monitor
Detect packet loss or latency spikes that can break long-lived SSH sessions.
Traceroute Map
Identify routing issues or asymmetric paths between client and server.
ISP Support Insights
Determine whether your ISP blocks or rate-limits SSH traffic.
When SSH Is Not the Problem
- Server CPU or memory exhaustion
- Disk full preventing shell startup
- Authentication delays due to LDAP/SSSD
Escalation Checklist
- Port scan results
- Traceroute to SSH endpoint
- Latency and loss measurements
- Exact error messages and timestamps