In this article I describe No IP Domain Lookup Command of IOS in Cisco Routers and switches. Basic commands of IOS in Cisco Router relates to set the hostname, password etc on first time. The result of basic commands of IOS in Cisco Router initially saved in running configuration and we need to copy the running configuration into the startup configuration. The No IP Domain Lookup Command of IOS in Cisco Router run by the CLI command lines. IOS is acronym for Internetwork Operating System which is related to Cisco networking devices. IOS Internetwork Operating System provides the facility to run the No IP Domain Lookup Command of IOS of Cisco Router.
The configuration remain save in IOS memory via two way running and startup configuration. Basically running configuration is the settings which are running when a router is in functional condition. It is not necessary the running configuration remain save and come back when the router rebooted due to any reason. The startup configuration keep the setting in hard memory of router. Every time when router power on the startup configuration settings comes by default. The running configuration deleted automatically when the router goes power off. It is just like working with RAM and ROM.
The network administrator can change the configurations by basic commands of IOS in Cisco Router and maintain the networking device in a network by using Cisco IOS commands. IOS is an application which run as operating system for the networking devices like router or switch. Command Line Interface CLI in Cisco IOS provides a command line interface to a remote computer with various Cisco IOS command modes for network administrator. IOS load after a fix booting sequence every time when we boot the router or switch. On booting the router the startup configuration load in to the RAM of router So before learning about the Basic commands of IOS lets see some basic fundamentals of IOS Internetwork Operating System. You can also read the IOS booting sequence here.
No IP Domain Lookup Command of IOS Necessity
IOS Internetwork Operating System is a Cisco propriety for Cisco networking devices like routers and switches. Network administrator can work with various Cisco IOS command modes of any networking device from a computer in the network. It is very helpful to run the No IP Domain Lookup Command in Cisco Router when a router need to be installed in the network. The purpose of No IP Domain Lookup Command is to avoid the search unknown string in the CLI. All the routing configuration and other settings saved in the IOS Internetwork Operating System of router. Before going to learn about the No IP Domain Lookup Command in Router lets see some basic terms related to the IOS.
IOS Internetwork Operating System provide to do any changes on any interface or the router or switch. IOS Internetwork Operating System allowed to maintain the networking device from a very far location remotely. The IOS of Cisco can be integrated with other networking devices like IBM and SNA. The Cisco IOS command modes are very user friendly, the user can take the help about any command from CLI for a device.
The IOS Internetwork Operating System allow to configure the encryption, routing and authentication in the router or switches. IOS Internetwork Operating System have three variants XE, XR and Nexus. The XE version available with aggregation service routers and catalyst switches. XR version available with carrier routers. Nexus allow to configure the Nexus family devices. Before IOS Internetwork Operating System Cisco run the CatOS on its networking devices. IOS Internetwork Operating System is operating system independent means you can run the IOS on windows as well as on Linux or Unix operating system. The IOS developed in the decade of 1980 for Cisco routers.
Types of memory used to run the No IP Domain Lookup Command
There are multiple types of memory available in the router which takes part in the IOS Internetwork Operating System to run the No IP Domain Lookup Command in Cisco Router. It is necessary to know about the various types of memory used in router for various purpose. We can say that each memory is responsible for different task for the IOS Internetwork Operating System. A Cisco router contains four main memories RAM, ROM, NVRAM and Flash memory.
RAM stands for Random Access Memory which is like a RAM in any computer. In a Router, RAM stores the running configuration and routing table with routing protocol. The IOS loaded in the RAM After the completion of IOS Booting sequence in the router. RAM stores the data until the router is power ON. After shutting down the router, all data stored in RAM will erase automatically.
ROM the Read Only Memory stores the data permanently in it. The ROM loaded the previously saved configuration in IOS Internetwork Operating System of router. Mostly the bootstrap start up program stored in ROM. The initial function known as POST is also stored in ROM and run during the first step of IOS Booting sequence in router.
NVRAM memory is a type of RAM but it is Non-Volatile. The data saved previously in the NVRAM loaded after completion of IOS Booting sequence in router. It means the data stored in it doesn’t depends on Power on or off. We can write the data multiple times on it. ROM is read only memory. The main difference between NVRAM and ROM is that data of NVRAM can be changed by configuration.
Another type of memory available in router is Flash memory. Flash memory keep save the IOS image. Flash memory is read and writable memory. In case of any error in the IOS Booting sequence the image of IOS can be used for booting the router.
The Basic commands of IOS in detail including No IP Domain Lookup command
Some basic configurations of Cisco Router are necessary to set first time. These basic configurations provide the information of router and allow you to access it. No IP Domain Lookup Command is one of basic commands of IOS which can be used again and again during working with the CLI of a router or switch. The No IP Domain Lookup Command tells the router not to search any wrong words typed in the CLI.
There are a lots of commands available in Cisco IOS for various configurations. In this article I discuss about No IP Domain Lookup Command. I will also describe that How to use command Line interface perfectly. As we know there are three command modes in Cisco IOS. You can read the full article related to command modes here.
No IP Domain Lookup Command in brief
No ip domain lookup command disable the DNS lookup function in a router. In this article i describe this command with examples. DNS lookup function allows router to searched the in corrected commands. By default the DNS lookup function enabled and every time when a command passed to router’s CLI it will check the command. If there is any DNS server available in the network this function is useful. Without DNS server router try to find the wrong command and take time. To avoid this delay in command we disable the DNS lookup.
The hostname of router in this article is ccnatutorials.
ccnatutorials>c Host: c Translating "c"...domain server (255.255.255.255) % Unknown command or computer name, or unable to find computer address ccnatutorials>
The above translating cause a lot of delay to back to prompt.
What is DNS lookup ?
DNS resolved the domain name. When a wrong command is passed to Cisco router, router search for DNS server in the network. This cause a lot of delay for user. To disable the DNS lookup “no ip domainlookup” command used in Cisco router. You can see the status of DNS lookup by show running-config command in privilege mode. See the below example.
ccnatutorials#show running-config Building configuration... Current configuration : 637 bytes ! version 15.4 no service timestamps log datetime msec no service timestamps debug datetime msec no service password-encryption ! hostname ccnatutorials ! ip cef no ipv6 cef ip domain-lookup ! spanning-tree mode pvst interface GigabitEthernet0/0/0 no ip address duplex auto speed auto shutdown !
no ip domain lookup command
no ip domain lookup command can be run from global configuration command mode. After running no ip domainlookup router will not check the wrong command in DNS. So you save the time which taken by the router. See the below example on both stages DNS lookup enable and disable.
How to run no ip domain lookup command ?
To run no ip domain lookup command go to Global configuration mode and run command. After running the command come back to user command mode and write the configuration. See the example ahead.
ccnatutorials(config)#no ip domain lookup ccnatutorials(config)#exit ccnatutorials#wr Building configuration... [OK] ccnatutorials#exit ccnatutorials>
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