Configuration Template

# Base configuration: define the alias and the default authentication method
Host custom-alias
    User your-username
    PreferredAuthentications publickey
    IdentityFile "path/to/your/private_key"

# Internal network route: detect whether the internal network is reachable via ping
Match host custom-alias exec "ping -n 1 -w 100 internal.ip >nul 2>&1"
    HostName internal.ip
    Port internal_port

# External network route: fallback when the internal network is unreachable
Match host custom-alias
    HostName external.ip
    Port external_port

Usage Steps

1. Replace the configuration values

   • custom-alias: set an alias that's easy to remember
   • your-username: replace with your login username
   • path/to/your/private_key: replace with the path to your private key file
   • internal.ip: replace with the internal IP address
   • internal_port: replace with the internal port
   • external.ip: replace with the external IP address
   • external_port: replace with the external port

2. Connection command

   BASHCopy

   ssh custom-alias
   

How It Works

1. The SSH client receives a connection request for custom-alias
2. It checks the Match conditions in order:
   • First it runs the ping command to test connectivity to the internal network
   • If the internal network is reachable, the internal configuration is used
   • If the internal network is unreachable, the external configuration is used
3. It connects using whichever configuration applies

Notes

• Windows system paths use backslashes \
• Linux/Mac system paths use forward slashes /
• ping command arguments:
  • Windows: ping -n 1 -w 100
  • Linux/Mac: ping -c 1 -W 1
• Make sure the configuration file has the correct permissions (600 is recommended on Linux/Mac)