SecurityGlobal Config

ip domain-name [domain]

Configures the default domain name appended to incomplete hostnames during DNS resolution, enabling the router to resolve unqualified names into fully qualified domain names.

Syntax·Global Config

ip domain-name [domain]

When to Use This Command

Setting a domain name for a small office router so that pinging 'server1' resolves to 'server1.example.com'.
Configuring a domain name for SSH key generation, as the domain name is required for RSA key pair creation.
Defining a domain name for a branch office router to simplify hostname resolution in a corporate network.
Using with 'ip name-server' to ensure DNS queries use the correct domain suffix.

Command Examples

Basic domain name configuration

ip domain-name example.com

No output is generated; the command sets the domain name to 'example.com' in the running configuration.

Verifying domain name configuration

show running-config | include ip domain-name

ip domain-name example.com

The output displays the configured domain name. If missing, DNS resolution for unqualified names will fail.

Understanding the Output

The 'ip domain-name' command does not produce output upon execution. To verify the configuration, use 'show running-config | include ip domain-name' which displays the domain name if set. If no domain name is configured, the line will be absent, and the router will not append a domain suffix to unqualified hostnames. This can cause DNS resolution failures for names like 'server1' unless a fully qualified domain name is used.

CCNA Exam Tips

CCNA exam tip: The 'ip domain-name' command is required before generating RSA keys with 'crypto key generate rsa'.

CCNA exam tip: Without a domain name, the router will not append a suffix to hostnames, so 'ping server1' will fail unless 'server1' is in the hosts table.

CCNA exam tip: The domain name is stored in the running configuration and can be verified with 'show running-config | include domain'.

CCNA exam tip: The command is global configuration mode; ensure you are in the correct mode before entering it.

Common Mistakes

Mistake 1: Forgetting to configure 'ip domain-name' before generating SSH keys, leading to an error 'No domain name configured'.

Mistake 2: Using 'ip domain-name' with a trailing dot (e.g., 'example.com.') which is incorrect and may cause DNS issues.

Mistake 3: Confusing 'ip domain-name' with 'ip domain-list' which adds multiple domain suffixes for DNS resolution.

Related Commands

crypto key generate rsa modulus [bits]

Generates an RSA key pair for SSH, encryption, or digital signatures on a Cisco IOS device, typically used to enable secure management access.

show running-config

Displays the current active configuration in DRAM, showing all non-default settings.

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