Cisco 10000 Series Routers

Document ID: 46253

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Host to IP Address Translation
      Why "Translating.... domain server (255.255.255.255)" Messages Occur
      Disable Host to IP Address Translation to Prevent "Translating..... domain server (255.255.255.255)" Messages
      Verify
Related Information

Introduction

This document addresses the issue of translating….. domain server (255.255.255.255) messages appearing on the router after an invalid command is entered in user or enabled mode.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Host to IP Address Translation

Why "Translating.... domain server (255.255.255.255)" Messages Occur

By default, when a command in user or enable mode is entered into a router and this command is not recognized, the router believes that this is the host name of a device that the user is attempting to reach using telnet. Therefore, the router tries to resolve the unrecognized command into an IP address by doing an IP domain lookup. If no specific domain server has been configured on the router, the router will issue a broadcast for the command to be translated into an IP address. It can take several seconds for the router prompt to return while the router waits for a response to its Domain Name System (DNS) broadcast.

Note: You can also use the transport preferred none command on the vty/con/aux lines to prevent the router from attempting to resolve an invalid command into an IP address. The DNS information is available in the output of other commands. However, when you have to initiate a telnet session from the router, place the telnet keyword before the hostname, since the router does not telnet automatically when you type a hostname. Remember to add the ip name-server command to specify the address of the name server.

The following are examples of the default router behavior in user and enable mode.

User Mode

R1>xxxx

Translating "xxxx"...domain server (255.255.255.255)

(255.255.255.255)

Translating "xxxx"...domain server (255.255.255.255)

% Unknown command or computer name, or unable to find computer address

R1>

Enable Mode

R1#xxxx

Translating "xxxx"...domain server (255.255.255.255)

(255.255.255.255)

Translating "xxxx"...domain server (255.255.255.255)

% Unknown command or computer name, or unable to find computer address

R1#

Disable Host to IP Address Translation to Prevent "Translating..... domain server (255.255.255.255)" Messages

To disable the default behavior of the router of attempting to resolve the invalid command into an IP address, enter the no ip domain-lookup command in global configuration mode.

Verify

To verify that the domain lookup has been disabled, enter an unknown command into the router in user or enable mode. The user will immediately receive a router prompt without the router issuing a DNS broadcast. Below is an example:

R1#xxxx

Translating "xxxx"

Translating "xxxx"

% Unknown command or computer name, or unable to find computer address

R1#

Related Information

• Understanding the Domain Name System
• Configuring DNS on Cisco Routers
• Technical Support - Cisco Systems