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SSH vs Telnet: what is the difference?
In short: Telnet and SSH both give remote command-line access to network devices and servers. Telnet sends everything, including passwords, as readable text, so anyone on the path can capture it. SSH encrypts the whole session and supports stronger sign-in methods such as keys, which is why it is the standard today.
SSH vs Telnet in one sentence
SSH (Secure Shell) gives an encrypted remote command-line session, while Telnet gives the same kind of access with no encryption at all.
Side-by-side comparison
| Feature | SSH | Telnet |
|---|---|---|
| Encryption | Yes, the whole session | None: plain text |
| Default port | TCP 22 | TCP 23 |
| Passwords on the wire | Encrypted | Readable by anyone capturing traffic |
| Sign-in options | Password or key pairs, plus MFA | Password only |
| Server identity check | Yes, using host keys | No |
| Extra features | Secure file copy and tunnelling | Very basic |
| Use today | Standard for remote management | Avoid, except in isolated labs |
What is SSH?
SSH creates an encrypted connection between your computer and the device you are managing. Before you sign in, the server proves its identity with a host key, so you know you are talking to the right machine. You can sign in with a password or, better, a key pair. Network engineers use SSH every day to configure Cisco routers and switches, Linux servers and firewalls. It also powers secure file transfer tools.
What is Telnet?
Telnet is one of the oldest internet protocols, from a time when networks were small and trusted. It simply passes your keystrokes and the device's replies back and forth with no protection. A packet capture tool such as Wireshark can show a Telnet password in seconds. You may still see it on very old equipment or in training labs.
Which one should you use?
Always use SSH for real networks. On Cisco devices that means setting a hostname and domain name, generating RSA keys, creating a local user and setting transport input ssh on the VTY lines so Telnet is refused. Use Telnet only inside an isolated practice lab, if at all. Our switch hardening playbook covers this step by step.
Common mistakes and myths
- "Telnet is fine on an internal network." Attackers who get inside can capture it just as easily.
- Leaving both SSH and Telnet enabled. Disable Telnet completely.
- Ignoring host key warnings. A changed key can mean you are connecting to the wrong device.
- Using SSH with a weak password. Use long passwords or keys, and limit who can connect.
Learn more
Key takeaways
- Both give remote command-line access to devices.
- Telnet sends everything, including passwords, in plain text.
- SSH encrypts the session and checks the server's identity.
- Disable Telnet and allow only SSH on real equipment.
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