Reply to post: Re: It's bad to say....

OK, this time it's for real: The last available IPv4 address block has gone

Lee D Silver badge

Re: It's bad to say....

I always use a subnet calculator ( Anything else is just going to introduce errors, because a lot of things WILL still work with an incorrect subnet.

For instance, the range I inherited was 48.0/22 ( - that's a really odd range.

They were using the 48's for client DHCP initially (again - NO IDEA WHY, it's within a local range!). Then they needed more addresses, so some fool decided to do the above (which gives you the 48.49.50 and 51's). But they didn't update the subnet everywhere. So what you get are a lot of computers that can get an IP, log on, talk to the gateway, connect to the Internet, etc.

But when you try to talk to printers or, say, anything broadcast - DLNA, Chromecasts, Airplay, etc. then it doesn't work properly.

And you get things like... the 48's are filtered for web, but the rest aren't. All kinds of issues. And I guarantee you that the CCTV, access control, etc. guys will just read it as their bog-standard, "we-don't-know-why-just-type-it" no matter how much you highlight the fact because they don't understand what a subnet is (or a VLAN or VPN or STP or anything, for that matter).

The solution, of course, is to stop faffing about and use well-known subnets. Very few places have IT big enough to worry about broadcast floods, etc. and hence want to limit their subnets down to the bare minimum necessary, but no IT department that understands the issue... just use the whole damn range and a bog-standard subnet and be done with it.

Then you have the numbering issues? Then don't. Nobody needs to care about IP addresses any more. I wouldn't be able to tell you the IP address of any of the 1000+ devices on my networks except for a) the gateway, b) the primary and secondary DNS, c) the main DC (which is actually the primary DNS anyway, but I don't actually NEED to know that, I could just use it's name!).

At home is the same. My router gives everything a name. Sure, at one point you have the IP there but it's DHCP and then you "reserve" the lease and it's permanently on that address but... more importantly... you then just give it a name. Anything that doesn't have a name will autodiscover, I assure you (e.g. Chromecasts by using the broadcast address).

And it's a damn sight easier for grandpa to remember to type in "backup" into his browser than "" for his backup NAS, or cctv, or printer whatever else.

As far as I'm concerned, if I don't need to know anything more than gateway and DNS (the two things you really CAN'T refer to by a DNS name), then nobody else does either. I've memorised my VLANs and subnets on each VLAN, though. That matters. But the IP of individual machines? Nope.

And, to be honest, it REALLY shouldn't matter. Anything that needs to talk to a server should be using the name. Because then transition and retirement is much easier because you just change what the name resolves to without having to have two machines with the same IP trying to failover to each other etc. as you make the switch. Anything else should be picking up a random from DHCP, or literally a "fill-in-the-gap" on your static lists as necessary.

Too many simple problems are caused by referring to machines DIRECTLY by IP or MAC. Whereas we solved that problem for the Internet by making them all invisible behind a chosen nomenclature.

Do you know, I don't even know my outside static IP. Because it literally doesn't matter as NOWHERE is it referred to, except the DNS records of my domain. And yet I have a dozen or more outside services for hundreds of users.

Make your life simple. Choose simple, well-known subnets (the entire 10.0 range is perfectly fine for a local network, nobody will ever have that many devices that it will matter, without having a switch capable of handling such things). Name everything. Use the .1 and .2 as gateway, DNS, etc. done.

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