On Sun, Jun 4, 2023 at 6:05 PM Antony Stone
<Antony.Stone@???> wrote:
>
> On Monday 05 June 2023 at 00:08:13, o1bigtenor via Dng wrote:
>
> > Should I switch my present router from 192.168.1.1 to my chosen
> > 172.16.x.x (I'm running on dd-wrt)?
>
> There is nothing inherently special about "192.168" or "172.16".
>
> These used to fall into what were called "Class C" and "Class B" networks
> respectively (and 10.0.0.0 was in Class A).
>
> However these days everything is done based on netmasks (you'll come across
> the abbreviation CIDR as well, meaning Classless Internet Domain Routing,
> emphasising that the old Classes are no longer relevant).
>
> Basic guide to netmasks:
>
> 1. 255.255.255.0 means that the first three numbers in the IP addresses on your
> network are fixed (every machine has the same first three numbers in its
> address) and the last number can be anything between 0 and 255.
>
> 2. 255.255.0.0 means the first two numbers are fixed, and the last two can each
> be anything between 0 and 255.
>
> 3. I won't for the time being discuss netmasks which contain numbers other
> than 0 or 255.
>
> At this point it's useful to note that two addresses "disappear" from every
> network range and cannot be assigned to machines on the network - the first
> address and the last address. That means that a network of 255.255.255.0
> which appears to leave you 256 addresses to play with, actually supports
> "only" 254 machines.

I seem to remember that 0.0, 1.1 and 255.255 were reserved from any group.
not allowed to use the 0.0 and the 255.255 as you mention and that 1.1 is the
router's address.
>
> Similarly, a netmask of 255.255.0.0, which leaves 256 x 256 = 65536 addresses
> to play with, can have up to 65534 machines on the network.
>
> Now, the interesting bit for you is that the entire range of addresses
> 192.168.0.0 up to 192.168.255.255 have been reserved (in document RFC 1918)
> for "private use", and there is nothing to stop you deciding "right, I'll use
> all of them, then" and setting your netmask to 255.255.0.0
>
> That means you can have up to 65534 machines on your network using addresses
> which all start with 192.168, just so long as every machine on the network has
> a netmask of 255.255.0.0 (at present you'll be using 255.255.255.0).
>
> So, to come back to the question you wanted to ask, which I've interpreted as
> "should I change my router's IP address from 192.168.1.1 to something in the
> 172.16.x.x range so that I have more IP addresses to play with?", my answer is
> "no - just change your netmask to 255.255.0.0 and carry on using 192.168.1.1
> for your router's address".
>
> The only two addresses in the range which you cannot use are 192.168.0.0 and
> 192.168.255.255.
>
> I think the rest should be sufficient for your needs - however I do wonder what
> size switches you have to join this lot together with :)

I'm thinking that I'll land up using a whole pile of something like 16 port
unmanaged switches - - - cheap and sorta inflexible but still useable.
Then the idea is to chain them together.

The big question is - - - if I'm using this 192.168.1.1/19 setup - - -
can I do this from 1 (!!) router?

(If this was all high speed data I wouldn't be asking - - - most of this
stuff is say a chunk of data every 0.5 second which to networking
is sorta slow and as there might be only 4 bytes of actual information
that isn't a lot of bandwidth.)

TIA