macOS 15.1.1 Internet connection issue

Are you able to create/modify the ESET firewall rules? Since you mention disabling its firewall solved the problem.

It may be possible to add firewall rules for both DNSResponder (primarily uses UDP port 53 for DNS queries and multicast traffic) & configd (typically uses various ports for DHCP, network configurations, and other dynamic protocols.)

One option, if you are familiar with Wireshark, would be for you to do a data capture to see where these protocols are hung up.

Sorry, I'm not well-versed with ESET so I can't offer much else. I don't think Apple will be much help at this time either as I don't see them "fixing" macOS for this issue. Good luck!

Read and heed this user advice:

Effective defenses against malware and ot… - Apple Community

Uninstall third party apps that claim to protect, etc. Such apps are are not needed and they may cause problems.

There are 2 Categories of Third Party Software / Services that are baffling to me.

Why some users insist on installing and using the below software. 

In no special order 

Commercial VPNs 

They may not be what one believes they are doing for the computer and what they actually are doing behind the scenes 

https://gist.github.com/joepie91/5a9909939e6ce7d09e29

Third Party Security Software 

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The Operating System resides in a Sealed and Read Only Volume that cannot be opened by the User nor by Third Party Applications.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

This will include  ESET ⬅️

Security. Built right in

Mac app security enhancements

The Built in Security  is all that is required to protect the computer.

Protecting against malware in macOS

lllusion wrote:

I don’t understand why people sat there are no viruses or malware that affect macOS. There are. Also, I’ve had ESET stop and quarantine files with known viruses.

Other than that, I’m in agreement to avoid all the well known third party AV’s etc. I’ve seen them cause more problems than they’re supposed to fix.

If we objectively review all the posting in the User's Question

At no time has there been an assertion that Malware / Adware does not exist and affect Apple Computer

Even the article the user has provided has made the distinction

The difference being, a software Virus has the Ability to Self Replicate where as Malware / Adware does not

" Before we run through the malware that’s been spotted on Macs we need to address this question. The word virus gets used a lot more than it should be – a more accurate word would be malware. A computer virus is so-called because it is capable of replicating itself and spreading. A virus is only one type of malware of which there are many, and unfortunately there have been cases on the Mac.  "

There is Adware & Malware which will affect the computer and is generally downloaded from “ Shady “ Websites or Developers who Inject this software into the download.

From a well written User Tip from @Kurt Lang

What is malware? - Apple Community

ESET is extremely unnecessary. I'd remove it asap according to their instructions for removal. After doing so your connectivity problems will go away. No anti-virus software is needed in macOS. Occasionally malware can arise and the only app that really is recommended is Malwarebytes. No other clean up or optimizer apps like clean my mac are needed either. They more than not, end up causing more problems than they claim to fix.

Curious in your first scenario, if instead of using a URL in a web browser to access a site over the Internet, you enter the site's actual IP address, can it access it now?

A simple site to try is Cloudflare @ 1.1.1.1

lllusion wrote:

Clearly ESET Cyber Security v8.2.800.0 and something in 15.1.1 are not playing well...I don't understand is why this started with macOS 15.1.1 (the issue did not occur with 15.1) and why it only occurs on one network and not another. ESET is not being helpful with the matter and keeps deflecting to the user to create rules to allow traffic. 🙄

ESET's web site says

Operating system: macOS Big Sur (11) to macOS Sonoma (14)

Does not mention Sequoia compatibility. It is up the developers to make sure their software works with the MacOS, not the other way around. So this is an example of how the cure was worse than the disease, e.g. software that is supposed to protect you from being shut down, instead shut you down itself. You are better off without it, unless you want to go through this repeatedly with MacOS updates in the future.

Turn off the busted Firewall as well

Stop using any VPN you are using.