Symptoms
The Dell Integrated Dell Remote Access Controller 9 (iDRAC9) firmware version 5.10.00.00 introduced HTTP and HTTPS connection changes. These changes may impact user connections when specifying a Fully Qualified Domain Name (FQDN) address. Due to these changes, iDRAC9 users may encounter connection errors, redirection, or '400 - Bad Request' errors. These connection sightings occur when the specified FQDN does not match the iDRAC 'DNSRacName' or 'DNSDomainName' values.
Browser Error Example:
Figure 1: Mozilla HTTPS header error Curl Error Example:
root@rhel7-vm:~$ curl -k https://iR640-A.dell.com/
Bad Request
Access Error: 400 -- Bad Request
Cause
The webserver in iDRAC9 firmware version 5.10.00.00 enforces an HTTP and HTTPS Host Header check by default.
Resolution
NOTE: To see images of the process used to configure the DNS, iDRAC Name, and Static DNS Domain Name correctly in the user interface see: How to configure the Integrated Dell Remote Access Controller 9 (iDRAC9) with Lifecycle Controller network settings?
By default, the iDRAC9 checks the HTTP and HTTPS Host Header and compares to the defined 'DNSRacName' and 'DNSDomainName'. When the values do not match, the iDRAC refuses the HTTP and HTTPS connection. In iDRAC9 5.10.00.00, this Host Header enforcement can be disabled with the following RACADM command.
#Disable host header check
racadm set idrac.webserver.HostHeaderCheck 0
Note: Only set the HostHeaderCheck value to '0' when a manual Host Record exists within the DNS environment.
When HTTP and HTTPS Host Header check is enabled (more secure), iDRAC can be accessed using the IPv4/IPv6 address, the RAC Name and the defined iDRAC FQDN (DNSRacName.DNSDomainName). If the end-user is accessing with hostnames that the iDRAC may not be aware of (such as manual DNS entries added in DNS records), iDRAC9 5.10.00.00 firmware version introduced a new attribute 'ManualDNSEntry'. This new setting can be updated with up to four IP addresses and host names/FQDNs to provide an allow-list of Host Headers. This ensures that incoming requests are not dropped when the HTTP and HTTPS Host Header carries one of the entries in the 'ManualDNSEntry' setting.
# Add manual entry to allow list
racadm set idrac.webserver.ManualDNSEntry 192.168.20.30
racadm set idrac.webserver.ManualDNSentry 192.168.20.30,idrac.mydomain.com
This additional configuration is required in cases such as when:
End user is using manual DNS configuration to access iDRAC (Manual DNS Host Record)Subject Alternative Name/Wild card certificate is used to access the iDRACAccessing iDRAC using host IP address directly (usingISM)
Note: To resolve ISM connection problems, disabling the host header check feature is the only mitigation. Manual DNS Entries do not resolve ISM connections.
