hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures a Cisco router for SSH…
An engineer configures a Cisco router for SSH access. The router has an IP address on interface GigabitEthernet0/0, and the engineer generates RSA keys using the command 'crypto key generate rsa modulus 2048'. However, SSH connections fail with 'Connection refused'. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the prerequisite order for SSH configuration, trapping candidates who focus on VTY transport settings or key modulus size instead of the fundamental requirement of a domain name for RSA key generation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The hostname and domain name are not configured.
SSH requires a fully qualified domain name (FQDN) to generate RSA keys. Without a configured hostname and domain name, the 'crypto key generate rsa' command may appear to succeed but actually generates default keys that are not bound to the router's identity, causing SSH to refuse connections. The 'ip domain-name' and 'hostname' commands are prerequisites for proper RSA key generation and SSH operation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The hostname and domain name are not configured.
Why this is correct
Correct because SSH uses the hostname and domain name to generate the RSA key pair; without them, the SSH server may not function.
- ✗
The VTY lines are not configured with 'transport input ssh'.
Why it's wrong here
Incorrect because even without 'transport input ssh', SSH would still attempt to connect; the refusal indicates the SSH server is not running.
- ✗
The RSA key modulus is too small.
Why it's wrong here
Incorrect because a modulus of 2048 is sufficient and supported.
- ✗
The IP address on GigabitEthernet0/0 is not in the same subnet as the client.
Why it's wrong here
Incorrect because the scenario does not mention connectivity issues; the refusal is at the application layer.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.