Peter Alcibiades wrote:
One moderate spec machine, now a few years old and in need of renewal, with two network cards. One card is DHCP to the one-port router, which goes to the ADSL connexion, which is fairly lightly used. This is getting an address in the range 192.168.0.x, as usual.
the other card is set up for static addressing, runs off an independent hub, and its using the range 172.16.0.1, with a subnet mask of 255.255.0.0.
I was all set to find that there was some huge network behind this, but in fact all there is is two printers. Yes, this network has one computer and two printers and appears to be using an internal Class B address for it, if I understand the situation correctly.
This is commonplace for people that don't fully understand the subnets, they see that there is a class B range on 172.16.0.0 and for some reason assume that it is mandatory that this needs to be a class B subnet, also I think a lot of GUI network configuration stuff will actually default to that if you specify an address in the class B range.
The same people moan at me for operating a class C range on 10.200.0.0 at home (mostly to avoid some clients internal subnets so I don't run into routing issues with VPN's) , stating that it should be class A
Like, if I really wanted to have the two printers on a separate net, why not just use a subnet mask of 255.255.255.128 and get two subnets that way? But in any case, why make life complicated with subnets, why would I not just assign them addresses in the 192.168.0.x range. What I usually have done in these situations (but I'm an amateur at this stuff nowadays) is put the printer on a static address of 192.168.0.100, have the router assign addresses to the computers in the low numbers, and everyone seems to print just fine. There are only two printers and one computer here, so what could the problem be?
It seems that the simplest thing to do is take all this stuff out and use a 5 port router/modem, and just make the two printers 101 and 102, why would this not work?
Yes for that size network I would agree. The consumer grade of router tends to struggle if ask the NAT to deal with two many hosts on the private side but for such a small number of machines it would be fine.
I think in this case the most likely thing is that the 172.16.0.0 network already existed and then they added the router, not really knowing what was going on and rather than put one in the others range they ended up with the above arrangement. That or possibly the system was originally on a no-nat broadband service so they could only have one address on the "public" NIC.
Is this missing something obvious?
Not that I can see...believe me I have seen this and worse many times (including the recent new client who has a "private" subnet starting at 11.22.33.0)