Topic: Fun connection issues to the PSN when both the PS4 and PS5 are one the home network.

Let me start by saying I have been working Tech Support for a large company where no one talks to anyone for many years and so I take great pride in my troubleshooting skills. I am no networking genius but know that if the answer is easy, I would either have found it or I will feel like the most complete idiot on the face of this planet when it is shown to me

Quick context :
Got both a PS4 and PS5. When both are connected to my personal network, the PS5 works fine but the PS4 will not connect to the PSN.

How I know it is the PSN specifically :
None of the PSN applications that require online connection will work. The browser however works perfectly see the Netflix paradox for more info

Netflix Paradox :
I used Netflix because the PSN version of Netflix has a troubleshooter that lets you know if your application can connect to the Netflix servers and the PSN servers. All 3 Netflix servers reply positive but the PSN one does not. Bonus, on the PS4 browser, navigating to the Netflix webpage, Netflix works... Didn't I tell you this was a fun problem?

Remote Play Paradox :
The only thing I could use the PSN for was doing a remote play from the PS4 to the PS5. Strangely that is no issue.

So here are my thoughts :

Why I think it's not the network/ISP :
Everything I own connects fine, including the PS4 (it goes on the internet, only the applications wont, IMO because it cannot connect to the PSN). My router can accept 32 devices at once in theory and I have less than 8 connected at all time, less than 14 registered in total.

Why I think it is not the machine : The PS4 works fine and all the applications connect as soon as the PS5 is in rest mode, no need to even turn it off fully

What I have tried so far :

• Both systems have the most up to date software updates, both done automatically
• In actuality, the PS5 would be wired and the PS4 wireless but I have tried all combinations just in case Wired/Wired, Wireless/Wireless, Wired/Wireless and Wireless/Wired
• Used different PSN accounts on either of the devices both with and without PS+
• Made both my primary Playstations and removed it and tried only one or the other, at the moment both are removed.
• I have reset both the PS4, the PS5 and the router multiple times while testing the above.
  (edit : thanks JimbobLink) *applied static IP addresses to both machines

In case someone thinks it is relevant :

• my Wireless router is a D-Link DIR-605L and beyond some security like IP allocation, I have not touched the basic network.

So what am I forgetting?

Sounds like it could be a routing problem when both devices are on. As a test, you could try manually setting the IP addresses of both the PS4 and PS5 to something different, but within your local network address range.

@JimbobLink I put both under a static ip, added that step in what I did but I still have the same problem.

Any other ideas/test I could do to try to narrow it down?

@Chep Now you have static IP addresses you could try port forwarding each device in your router settings

Thanks @JimbobLink, did not have time to try over the holidays.

That seems to have fixed it. I assigned public ports and a private port to each Static IP and it seems to have resolved my issue for the moment.

I'm still perplexed as to why it was happenning though.

@Chep Sometimes routers just don't behave as you'd expect, and you have to manually tell them where to route traffic, as you have done. You might well find that a newer router does not have any issues like this.