# Failed to Add a Device in OpUtils - Unknown Host

## Problem

You get an error as "Unknown Host" when attempting to add a device in OpUtils.

## Cause

This is a common error message that you get when you add a device in most of the tools in OpUtils. When a device is added using its DNS Name, OpUtils first tries to resolve the IP Address of the device. When this fails, you will get this error message. The following could be the reasons:

1. There is no such device in your network.
2. The DNS Server is not updated with this device.

## Resolution

**Check for Spelling Errors**

Check whether this device being added is a valid device. If you are sure, check whether the device name has been spelled correctly or try adding using its IP Address.

**Update the DNS Server**

Check whether the DNS Server has been updated with the device details. A DNS record for this device has to be added in the DNS Server used by the computer where OpUtils is installed. To check this, you can use the following command from the command prompt and verify whether the IP is resolved. This should be done from the computer where OpUtils is installed.

```
nslookup <DNS Name>
```

If you are using any alternate DNS Servers, OpUtils will not be able to resolve the IP Address of the device; you should add the device using its IP Address.

**Applies to:** Network Monitor, MAC Address Resolver, DHCP Scope Monitor, Bandwidth Monitor

**Keywords:** unknown host, dns server, ip resolver fails, dns configuration, dns to ip fails, forward lookup fails, forward dns lookup

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