After updating iDRAC access to iDRAC from Web UI fails with HostHeaderCheck enabled

Updated iDRAC on 10 R640 systems from 3.21.26.22 to 7.00.00.181.

iDRAC was updated successfully on all 10 systems.

3/10 systems ran across issue with accessing iDRAC with error.

All 10 systems have the same exact version of iDRAC and BIOS.

Error accessing iDRAC using IP from browser:

Bad Request

Your browser sent a request that this server could not understand.

Additionally, a 400 Bad Request error was encountered while trying to use an ErrorDocument to handle the request.

Workaround:

We applied work around to disable HostHeaderCheck on the 3 systems, and that resolved the issue.

Our customer does not want this work around, because it's less secure.

I provided customer to execute “racadm set idrac.webserver.ManualDNSEntry 192.168.20.30  -> Replace the ip address with their iDRAC IP”

Followed by enabling HostHeaderCheck, but that did not resolve the issue.

Adding ManualDNSEntry did not resolve the issue with HostHeaderCheck enabled.

The only way we can access the iDRAC from Web UI is to disable HostHeaderCheck.

7/10 systems have no issue with HostHeaderCheck being enabled.

3/10 systems are at the same BIOS/iDRAC as the 7/10 systems that have no issue with HostHeaderCheck enabled.

Before the iDRAC update this issue did not exist on the 3 systems.

Need assistance to get the iDRAC Web access working with HostHeaderCheck set to enabled on the 3/10 systems.