Resolve iDRAC 'Bad Request' Issue

We've come across a few Dell PowerEdge servers where the iDRAC interface over HTTP/HTTPS yields a 400 Bad Request. Due to this, the web interface is completely unavailable. The root cause is the HostHeaderCheck additional security feature that they have added. In this guide, we'll look at a few ways of solving this issue.

Secure Fix

racadm via Installed OS

Make sure you have racadm installed onto the operating system that resides on your server.
1. If the server is a hypervisor, please make sure racadm is installed on it and not the guest virtual machines.
Issue the following command, replacing the $hostname with the iDRAC interface's actual hostname:
```
racadm set idrac.webserver.ManualDNSEntry $hostname
```

racadm via SSHing Into iDRAC

SSH into the iDRAC interface.
Issue the following command, replacing $hostname with the iDRAC interface's actual hostname:
```
set idrac.webserver.ManualDNSEntry $hostname
```

Insecure Fix

racadm via Installed OS

Make sure you have racadm installed onto the operating system that resides on your server.
1. If the server is a hypervisor, please make sure racadm is installed on it and not the guest virtual machines.
Issue the following command to disable the HostHeaderCheck:
```
racadm set idrac.webserver.HostHeaderCheck 0
```

racadm via SSHing Into iDRAC

SSH into the iDRAC interface.
Issue the following command to disable the HostHeaderCheck:
```
set idrac.webserver.HostHeaderCheck 0
```