While SSH tunneling works flawlessly on Windows via PuTTY, many developers encounter the frustrating open failed: administratively prohibited: open failed error when using:

• MacOS terminals (native or iTerm2)
• Cygwin environments
• Linux subsystems

This error typically occurs due to server-side security policies or client misconfigurations:

# Server-side causes
1. AllowTcpForwarding set to "no" in sshd_config
2. PermitOpen restrictions in authorized_keys
3. Port-specific forwarding limitations

# Client-side issues
1. Improper -L/-R flag syntax
2. Conflicting local port usage
3. Permission constraints

First verify your server configuration:

ssh -v -L 8080:localhost:80 user@example.com
# Check verbose output for clues

For MacOS/Cygwin specific workarounds:

# Alternative syntax that often works
ssh -N -L 8080:127.0.0.1:80 user@example.com

# If using jump hosts
ssh -J jumpuser@jumpserver -L 8080:target:80 finaluser@targetserver

If you have admin access, modify /etc/ssh/sshd_config:

AllowTcpForwarding yes
PermitOpen any
# Or restrict to specific ports:
# PermitOpen host:port host:port

Remember to restart sshd:

sudo systemctl restart sshd
# Or for older systems:
sudo service ssh restart

Create persistent tunnel configurations:

Host mytunnel
    HostName example.com
    User tunneluser
    LocalForward 5901 localhost:5900
    ExitOnForwardFailure yes
    ServerAliveInterval 30

Then simply run:

ssh -fN mytunnel

When all else fails:

• Try dynamic forwarding: ssh -D 1080 user@host
• Use autossh for resilient connections
• Consider VPN alternatives if tunneling is blocked

Remember that corporate networks often impose additional restrictions that may require administrator intervention.

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While SSH tunneling generally works flawlessly on Windows via Putty, many developers encounter the frustrating open failed: administratively prohibited: open failed error when using:

• macOS Terminal or iTerm2
• Cygwin environments
• Linux SSH clients

This error occurs when the SSH server actively rejects your tunnel request due to security restrictions. Common triggers include:

# Typical error message
channel 2: open failed: administratively prohibited: open failed

If you control the SSH server, modify /etc/ssh/sshd_config:

AllowTcpForwarding yes
PermitOpen any
PermitTunnel yes

Then restart SSHD:

sudo systemctl restart sshd  # For systemd systems
sudo service ssh restart     # For older init systems

When you don't have server admin access:

Method 1: Using -N Flag

ssh -N -L 8080:localhost:80 user@example.com

Method 2: Try Different Forwarding Syntax

ssh -L *:8080:localhost:80 user@example.com

Enable verbose mode to identify the exact failure point:

ssh -vvv -L 8080:localhost:80 user@example.com

• Firewall blocking the forwarded port
• Server has AllowAgentForwarding disabled
• Client using deprecated SSH protocol versions

For persistent tunneling needs, consider:

autossh -M 0 -N -L 8080:localhost:80 user@example.com

Or using persistent connections:

ssh -o TCPKeepAlive=yes -o ServerAliveInterval=60 [...]