Software Update is badged, but macOS 12.3.1 not available

Problem solved.

It was a DNS issue, combined with what appears to be a malfunctioning Apple cdn server at 173.246.128.80.

I changed the DNS server entries in my gateway router to use Quad9 (9.9.9.9 & 149.112.112.112), and speedy download of macOS installers has returned.

A few weeks ago, on the advice of a cybersecurity guy I know, I changed my DNS settings to use DNS servers from CIRA Canadian Shield. CIRA is the Canadian Internet Registration Authority. They manage the .CA TLD, among other things. They've spun up a DNS service that purports to protect users from malware, phishing etc., similar to what Quad9 does. For readers who want to know what DNS addresses not to use, the DNS addresses for the CIRA servers are 149.112.121.20 & 149.112.122.20.

Here's the result of a DNS lookup of the URL used by Apple for software downloads using the CIRA DNS.

Note that a single IP address is returned.

M1-MacBookAir:~ drc$ nslookup swcdn.apple.com 149.112.122.20
Server:		149.112.122.20
Address:	149.112.122.20#53
Non-authoritative answer:
swcdn.apple.com	canonical name = swcdn.g.aaplimg.com.
Name:	swcdn.g.aaplimg.com
Address: 173.246.128.80

Here's the same lookup done by Quad9 DNS.

M1-MacBookAir:~ drc$ nslookup swcdn.apple.com 9.9.9.9
Server:		9.9.9.9
Address:	9.9.9.9#53
Non-authoritative answer:
swcdn.apple.com	canonical name = swcdn.g.aaplimg.com.
Name:	swcdn.g.aaplimg.com
Address: 17.253.15.201
Name:	swcdn.g.aaplimg.com
Address: 17.253.15.203

Note that Quad9 returns a pair of IPs, both different than the one provided by the CIRA lookup.

A traceroute reveals the 17.253.x.x servers are somewhere in NYC.

The 173.246.128.80 server appears to be in Toronto.

I conclude that Apple's Toronto server or the network connections to it are problematic.

[Link Edited by Moderator]

Update:

Last night, I closed the lid on my MBAir and let it sleep on the update problem.

When I woke it up this morning, the SU badge had vanished.

I opened Software Update, which still reported "Your Mac is up to date", with 12.3.

Did a little googling to see if I could find any reports of others having problems getting the 12.3.1 update.

About a half hour later, the red badge on SU spontaneously reappeared.

Opened SU, and found that the 12.3.1 update was now available to be installed. So I clicked Install.

That led to another headache. Software Update started downloading the update. I think it indicated the update was about 2 GB in size. The progress bar moved quickly about 2/3s of the way. Then stopped dead. Time remaining was displayed as 10 minutes, then 15, then 20. I ran Speedtest to ensure my internet connection was still on-line. It reported download speeds of 275 Mbps, which is what my WiLAN normally provides. Other internet services were working fine. Apple's system status page reported no problems. But Software Update was totally stalled. Then after 10-15 minutes of no activity, the progress bar started moving again, v.e.r.y slowly. It took another 20-30 minutes for the remaining 1/3 of the update to download.

SU then proceeded to restart the Mac and installation proceeded. It was a lengthy process - 4 or 5 progress bars appeared sequentially. Eventually, a 'time remaining' estimate appeared below the progress bar. Apple's 'time remaining' estimates are notoriously unreliable, but at least gave me some hope that the update was progressing. 45 minutes remaining, 30 minutes, 15 minutes... Finally, the macOS login screen appeared. The MBA now reports 12.3.1. Mission accomplished.

Based on this experience, I surmise that Apple's distributed infrastructure for delivering software updates has some flaws. Recently, I've also encountered irregular performance obtaining iOS updates. Sometimes they download lickety-split, and sometimes take many minutes to complete.

@P.Philips,

Thanks for responding.

What are the "Other Methods" that you mention for obtaining macOS updates? I searched on Apple's Downloads web page here, and could find nothing posted for Monterey. I surmise that you must mean getting the full installer via the App Store? I tried that - the App Store launches the same daemon used by Software Update (softwareupdated). It reports that the download of the 12 GB installer for 12.3.1 is going to take "about 8 days"!

My WiFi is solid - my M1-MacBook is about 10 feet from an 802.11ac base station.

Speedtest measures download speed of 292 Mbps. (my internet service is fibre).

No other users on my LAN.

No anti-virus software. No VPN.

And the AppleTV application will happily stream video while softwareupdated is loafing about. The M1 chip has plenty of horsepower available to handle the download.

All fingers seem to point at Apple's cdn (content delivery network) being the bottleneck. My router reveals that the update is coming from a server in Toronto (173.246.128.80).

P. Phillips wrote:

Personally looked at the CIRA Site and fail to seen how they can claim to protect the user from Bad Actors . Malware, Adware.

The value proposition of the CIRA DNS resolver is that same as Quad9, OpenDNS, and other providers. They purport to collect a (growing) list of domain names that are known to be the source of malware, phishing attempts, or other nasty activities. They then blacklist those malicious domains. Any client DNS queries for such domains don't get resolved, thus protecting the client device from connecting and subsequently getting infected. It's an effective way to reduce the dissemination of some malware, but it's only as good as the list of bad IPs (which needs to be updated in real-time to really be any good).