The PC which is part of this pair suddenly lost internet access. It is cabled to the router. This old machine from the same hub, OK. It was reaching the router OK, but no internet access. It's on a fixed IP address. As a quick fix tried letting it sort itself out. Where of course it changed to DCHP - but still not working. Claimed it couldn't find the DNS server. Checks on drivers etc showed OK.
Seems Windows did an update a couple of days ago. Restored to before that and everything works again.
It's a relatively new (and expensive) Gigabyte MB.
Open a Command Prompt and type "ipconfig /all" on both PCs and compare the DNS Servers for both on the Ethernet adapter.
If you're using DHCP they should be the same. It is always possible that the first PC has the DNS Server entry to some historical IP address and not set through DHCP.
I do it slightly differently. I have all my network on DHCP, but have the DHCP server set to give the same IP addresses out to those MAC addresses each time they connect.
Unless you re-use addresses that happens anyway with DHCP, I don't think any system on my LAN has ever changed its IP and nearly all are assigned by my DHCP server.
I like to group them - so xxx.xxx.xxx.10 to .39 is available for PCs (5 of them), laptops (2), tablets (3). .40 to .49 for printers (2). .50 to .69 Satellite boxes (4), music players (2), smart TVs (2), other set-top boxes (2). .80 to .89 for mobile phones and so on, with .190 to .254 for home server ESXI host, Nethserver based Domain controller, storage server, email server, etc. and other virtual machines.
Plus, I want to be absolutely sure that no address changes when the network and everything attached is restarted, as satellite and set-top boxes need to access each other and the server, while the music players need to access the server - and a whole lot more.
We are a bit of a techie household - except for my wife who doesn't know how any of it works. It has made online, remote learning and working from home easy though, as there is no competition for machines to work on.
Yes, but when they reconnect they get the same IP back. E.g. I go away for weeks at a time with my laptop but when I come back home it always gets the same IP. This is how it's meant to work, the DHCP server *does* remember MAC addresses and will give the same address to the same device every time unless there's a very good reason for not doing so.
Having dabbled with static IPs in the past, I've been relying on DHCP on Win10. Most of the time it works, but it does occasionally have hissy fits that I have never really been able to explain. Random power cycling eventually sorts it, sometimes have to delete and reinstall printers too.
I've got something over 50 devices on my system now (including phones and laptops belonging to the kids when they visit), I can see subnets looming.
But if you have a power cut or switch the electric off to do some DIY, the server and a number of devices will all lose power and may not get the same addresses - they may, but there is no certainty.
I had the opposite problem, addresses being completely non-random. I relegated one of my satellite boxes to the conservatory, put a new one in the living room and restored the (OpenVIX) setup from disk - and found that restoring the old setup to the new box also copied the old MAC address to the new device, which I certainly did not expect!
There is certainty if you configure the DHCP server to assign a particular IP address to a particular MAC address. That is what is being said above by Chris, and it's how I do it too. I have absolute certainty of IP addresses for all devices except those used by visitors (and they come out of a small pool).
It was me that originally said that. My reading of Chris's post was that he was saying that they normally get re-assigned the same IP address anyway, without setting specific IPs in the DHCP server. Then I was saying that they may not if restarting the network and devices after a power out.
If the DHCP server remains powered all the time, and only the client is disconnected, then *most* routers will reassign the same IP. Generally this is an "ok" thing on home networks, although it can be a limitation where there are lots of guest devices that come and go, since you will run out of DHCP pool addresses eventually, and the router will be forced to reallocate IP addresses to new MAC addresses. So stuff works for a fair while before something breaks without warning. (like someone's HP wifi connected printer "vanishes" after many weeks of working just fine!)
If the router is powered off, then all bets are off, since it may have no non volatile record of the IP to MAC parings.
If you want to have static addresses, but have them allocated via DHCP[1], then you need to use the capabilities available in many routers to permanently bind an IP to a MAC address, and then save that in the routers non volatile configuration.
Lastly remember that not all SOHO routers are created equally - so do a more reliable job of address allocation than others.
[1] this being the industry preferred way of allocating static IP addresses on larger networks these days.
There is virtually absolute certainty, the DHCP server stores its information, it's not volatile, so even if you turn the DHCP server off it will come back looking the same.
That's not to say you shouldn't be explicit about things that you want to have fixed addresses, I have a printer specified in my DHCP server configuration so I can be absolutely sure it always has the same address.
Exactly what I've been saying all along, you'll just about always get the same IP for a device except when there's a very good reason for it being otherwise.
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