[VVF 9] A Quirky DNS Case-Sensitivity Issue in the VCF Installer

Issue

When deploying VMware Cloud Foundation (VCF), the installer performs strict environment validations before initiating the actual deployment. While these checks are great for preventing failed installations, you might occasionally run into an interesting quirk regarding DNS reverse lookups and case sensitivity.

A quick look at a validation error caused by this behavior and how to easily resolve it.

During the deployment wizard, specifically (in may case) in the VCF Operations configuration step, you are required to enter the FQDN for the Operations appliances. In our scenario, we entered the Operations primary FQDN using lowercase letters (vbops...). This is standard practice for many administrators, as DNS resolution is inherently case-insensitive according to RFC standards.

However, when we reached Step 6 (Validate & Deploy), the pre-flight checks halted, and the validation failed specifically on the DNS Resolution task.
The system threw the following error:

"Reverse lookup of IP Address [10.250.245.248] returned FQDN [VBOPS...] which does not match the FQDN [vbops...] supplied in the deployment specification"

The root of the problem is that the VCF Installer performs a strict, case-sensitive string match. Even though the DNS server successfully resolved the IP address via the PTR record, the DNS server held and returned the FQDN string in uppercase (VBOPS). Because the input in the deployment specification was lowercase, the installer saw this as a mismatch and failed the validation.

Solution

To fix this issue, the FQDN provided in the VCF deployment wizard must perfectly match the exact case of the FQDN returned by your DNS server's reverse lookup (PTR) record.

Here are the steps to resolve it:

1. Navigate back to Step 3 (VCF Operations) in the deployment wizard.

2. Update the Operations primary FQDN so that it is written in uppercase (VBOPS...), matching exactly what the DNS server expects.

3. Proceed back to Step 6 (Validate & Deploy).

4. Click on RE-RUN VALIDATIONS.

Because the deployment specification now aligns perfectly with the uppercase DNS response, the installer's string comparison succeeds.
The DNS Resolution check will now show as Succeeded, and you can proceed with the VVF deployment.

Quick tip: To avoid this during future deployments, always do a quick nslookup against your target IP addresses beforehand to verify the exact casing your DNS infrastructure is handing out for its PTR records!

Useful links:

– RFC 4343 - Domain Name System (DNS) Case Insensitivity Clarification (2006):
https://datatracker.ietf.org/doc/html/rfc4343

That's it.