ChatGPT makes me *less* confident about things I know little about
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I'll admit I have a lot of reading to catch up with to reach the level of understanding about networks that I'd like to have. Well, specifically, subnetting. After some going back and forth with ChatGPT for about half an hour (trying to get it to rephrase its answers to try to show it that previous answers were clearly wrong), I've only managed to become less certain about many things, but I'm hoping I've at least come to one correct conclusion: I want the valid IP range on my home network to be restricted to 192.168.X.Y, where X ranges from 1 through 31, and Y ranges from 1 through 254 (with the understanding that, for all intents and purposes, you never directly assign [whatever].0 or [whatever].255 to a device). So, the subnet I should be using is 255.255.224.0 (so for the third octet I could use everything between 1 through 31). What I haven't been able to get out of ChatGPT is whether a machine configured with an IP between 192.168.32.1 and 192.168.255.254 would fail to reach the rest of the systems on 192.168.[1-31].[1-254]. It *sounds* right to me, but until I try, I'm just guessing. Generally, I configure all of my systems with a static IPv4 address. And I want all systems within my network to be able to see each other, just to keep things simple. Am I right at least so far, with that subnet of 255.255.224.0? Further discussion: The idea is - for the third octet - the 255 devices under "1" would be my physical machines. My laptops would be under "2". Printers under "3". My first VM host would be at 10 (192.168.10.1). VMs it hosts would be 192.168.10.2 through .254. My second VM host would be 192.168.11.1; its VMs would range from 192.168.11.2 through 254, etc. Of course that leaves some big gaps within each range, but it does keep things organized (at least in my mind it does). I'm no network admin; do people segregate things this way?
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I'll admit I have a lot of reading to catch up with to reach the level of understanding about networks that I'd like to have. Well, specifically, subnetting. After some going back and forth with ChatGPT for about half an hour (trying to get it to rephrase its answers to try to show it that previous answers were clearly wrong), I've only managed to become less certain about many things, but I'm hoping I've at least come to one correct conclusion: I want the valid IP range on my home network to be restricted to 192.168.X.Y, where X ranges from 1 through 31, and Y ranges from 1 through 254 (with the understanding that, for all intents and purposes, you never directly assign [whatever].0 or [whatever].255 to a device). So, the subnet I should be using is 255.255.224.0 (so for the third octet I could use everything between 1 through 31). What I haven't been able to get out of ChatGPT is whether a machine configured with an IP between 192.168.32.1 and 192.168.255.254 would fail to reach the rest of the systems on 192.168.[1-31].[1-254]. It *sounds* right to me, but until I try, I'm just guessing. Generally, I configure all of my systems with a static IPv4 address. And I want all systems within my network to be able to see each other, just to keep things simple. Am I right at least so far, with that subnet of 255.255.224.0? Further discussion: The idea is - for the third octet - the 255 devices under "1" would be my physical machines. My laptops would be under "2". Printers under "3". My first VM host would be at 10 (192.168.10.1). VMs it hosts would be 192.168.10.2 through .254. My second VM host would be 192.168.11.1; its VMs would range from 192.168.11.2 through 254, etc. Of course that leaves some big gaps within each range, but it does keep things organized (at least in my mind it does). I'm no network admin; do people segregate things this way?
dandy72 wrote:
do people segregate things this way?
No, it is overkill. If the number of hosts is under 255, and I suspect for a home network this is the case, You can just use a traditional netmask like 255.255.255.0. If you want to "organize" hosts you can still do something like 1 to 30 computers; 40 to 100 VMs; printers, something else. If you set a netmask like you want 255.255.224.0, that is also, ok but it's not going to exclude the hosts with 0 and 255. So a host like 192.168.2.0 is perfectly acceptable Only the end for the range is going to be treated differently: the 192.168.31.255 is going to be the broadcast address for your network. Sub-netting is usually done for the exact opposite of your reason: when you want hosts not to be visible outside their own sub-nets. More thoughts: - set up a DHCP server for random things that land on your network (phones, friends, etc.). Give it a range distinct from your fixed hosts. - set up a DNS server and give meaningful names to your devices instead of relying on IP addresses. I'm using a RPi for both the DNS and DHCP server. It is more than enough for my needs.
Mircea
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I'll admit I have a lot of reading to catch up with to reach the level of understanding about networks that I'd like to have. Well, specifically, subnetting. After some going back and forth with ChatGPT for about half an hour (trying to get it to rephrase its answers to try to show it that previous answers were clearly wrong), I've only managed to become less certain about many things, but I'm hoping I've at least come to one correct conclusion: I want the valid IP range on my home network to be restricted to 192.168.X.Y, where X ranges from 1 through 31, and Y ranges from 1 through 254 (with the understanding that, for all intents and purposes, you never directly assign [whatever].0 or [whatever].255 to a device). So, the subnet I should be using is 255.255.224.0 (so for the third octet I could use everything between 1 through 31). What I haven't been able to get out of ChatGPT is whether a machine configured with an IP between 192.168.32.1 and 192.168.255.254 would fail to reach the rest of the systems on 192.168.[1-31].[1-254]. It *sounds* right to me, but until I try, I'm just guessing. Generally, I configure all of my systems with a static IPv4 address. And I want all systems within my network to be able to see each other, just to keep things simple. Am I right at least so far, with that subnet of 255.255.224.0? Further discussion: The idea is - for the third octet - the 255 devices under "1" would be my physical machines. My laptops would be under "2". Printers under "3". My first VM host would be at 10 (192.168.10.1). VMs it hosts would be 192.168.10.2 through .254. My second VM host would be 192.168.11.1; its VMs would range from 192.168.11.2 through 254, etc. Of course that leaves some big gaps within each range, but it does keep things organized (at least in my mind it does). I'm no network admin; do people segregate things this way?
Start thinking about subnet as a single number, such as 24 for 255.255.255.0. This makes your life easier, when working with subnets, not equal to 24 and 16.
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dandy72 wrote:
do people segregate things this way?
No, it is overkill. If the number of hosts is under 255, and I suspect for a home network this is the case, You can just use a traditional netmask like 255.255.255.0. If you want to "organize" hosts you can still do something like 1 to 30 computers; 40 to 100 VMs; printers, something else. If you set a netmask like you want 255.255.224.0, that is also, ok but it's not going to exclude the hosts with 0 and 255. So a host like 192.168.2.0 is perfectly acceptable Only the end for the range is going to be treated differently: the 192.168.31.255 is going to be the broadcast address for your network. Sub-netting is usually done for the exact opposite of your reason: when you want hosts not to be visible outside their own sub-nets. More thoughts: - set up a DHCP server for random things that land on your network (phones, friends, etc.). Give it a range distinct from your fixed hosts. - set up a DNS server and give meaningful names to your devices instead of relying on IP addresses. I'm using a RPi for both the DNS and DHCP server. It is more than enough for my needs.
Mircea
Some good thoughts in there, thanks for that. I probably do have less than 255 devices (VMs included), but if I want set ranges within a total max of 255 entries, it won't be long before I run out of space and just go back to having to find a gap somewhere, and it'll be ad-hoc again. I didn't bring DHCP into the discussion just to keep it simple. I do want to let my router assign (say) .1 through .25 for random devices that show up, but stick with static IPs for everything else that should "always be present".
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I'll admit I have a lot of reading to catch up with to reach the level of understanding about networks that I'd like to have. Well, specifically, subnetting. After some going back and forth with ChatGPT for about half an hour (trying to get it to rephrase its answers to try to show it that previous answers were clearly wrong), I've only managed to become less certain about many things, but I'm hoping I've at least come to one correct conclusion: I want the valid IP range on my home network to be restricted to 192.168.X.Y, where X ranges from 1 through 31, and Y ranges from 1 through 254 (with the understanding that, for all intents and purposes, you never directly assign [whatever].0 or [whatever].255 to a device). So, the subnet I should be using is 255.255.224.0 (so for the third octet I could use everything between 1 through 31). What I haven't been able to get out of ChatGPT is whether a machine configured with an IP between 192.168.32.1 and 192.168.255.254 would fail to reach the rest of the systems on 192.168.[1-31].[1-254]. It *sounds* right to me, but until I try, I'm just guessing. Generally, I configure all of my systems with a static IPv4 address. And I want all systems within my network to be able to see each other, just to keep things simple. Am I right at least so far, with that subnet of 255.255.224.0? Further discussion: The idea is - for the third octet - the 255 devices under "1" would be my physical machines. My laptops would be under "2". Printers under "3". My first VM host would be at 10 (192.168.10.1). VMs it hosts would be 192.168.10.2 through .254. My second VM host would be 192.168.11.1; its VMs would range from 192.168.11.2 through 254, etc. Of course that leaves some big gaps within each range, but it does keep things organized (at least in my mind it does). I'm no network admin; do people segregate things this way?
TL;DR; you are correct and devices with an IP of 192.168.32.0 (and up) would not be on the same subnet as a device with an IP of 192.168.11.1 ... so should not be able to communicate directly... and the TCP/IP stack(s) would/should try and "route" the packets via something that knows about "routing" (or in this case not at all because such subnet addresses are internal/private/non-routable) Oh boy, I hope I've got all these details correct :) I don't think of a subnet as a number... I always think of a subnet in terms of the binary mask... network mask ... 255.255.224.0 ... is ... 11111111.11111111.11100000.00000000 The 'network' of a device can be found by ANDing the device IP with that network mask (gives the subnet address). If I do the same with another device IP and I find that the resulting values (i.e. subnet addresses) are the same, then the 2 devices are on the same 'network/subnet' and can (copper and switches willing) communicate directly If the value I get after applying the mask is different then the devices are on different subnets and the TCP/IP stack will/should send it to something that can "route" between these subnets. So... 192.168.0.1 masked (ANDed) with the 255.255.224.0 pattern will be 192.168.0.0, or 11000000.10101000.00000000.00000000 192.168.31.1 masked with that pattern will be 192.168.0.0 ... same subnet is local so can communicate directly (and at which point ARP kicks in) 192.168.32.1 masked with that pattern will be 192.168.32.0 ... 11000000.10101000.00100000.00000000 (see the new 1 in the third octet which corresponds with a 1 in both the mask and the IP address) ... subnet values are different so different network/subnet, needs to be routed Of course, if the a router is set up in an interesting way, and knows how to route for both the 192.168.0.0/19 subnet AND the 192.168.32.0/19 network on the same piece of copper, then it might/should work (DHCP et.all. complexity though) And if a mask is set incorrectly somewhere (e.g. 255.255.0.0) that it'll maybe work one way and not the other And it all depends on the TCP/IP stack. I don't know whether ARP understands netmasks so whether a device on a different subnet is plugged into the same network cabling could obtain the hardware network address regardless of subnet... so this is more about routing than security. The good thing about doing it the way you want to is it makes you think about details, and not just plug simple numbers in like 255.255.255.0 ... all good fun :)
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I'll admit I have a lot of reading to catch up with to reach the level of understanding about networks that I'd like to have. Well, specifically, subnetting. After some going back and forth with ChatGPT for about half an hour (trying to get it to rephrase its answers to try to show it that previous answers were clearly wrong), I've only managed to become less certain about many things, but I'm hoping I've at least come to one correct conclusion: I want the valid IP range on my home network to be restricted to 192.168.X.Y, where X ranges from 1 through 31, and Y ranges from 1 through 254 (with the understanding that, for all intents and purposes, you never directly assign [whatever].0 or [whatever].255 to a device). So, the subnet I should be using is 255.255.224.0 (so for the third octet I could use everything between 1 through 31). What I haven't been able to get out of ChatGPT is whether a machine configured with an IP between 192.168.32.1 and 192.168.255.254 would fail to reach the rest of the systems on 192.168.[1-31].[1-254]. It *sounds* right to me, but until I try, I'm just guessing. Generally, I configure all of my systems with a static IPv4 address. And I want all systems within my network to be able to see each other, just to keep things simple. Am I right at least so far, with that subnet of 255.255.224.0? Further discussion: The idea is - for the third octet - the 255 devices under "1" would be my physical machines. My laptops would be under "2". Printers under "3". My first VM host would be at 10 (192.168.10.1). VMs it hosts would be 192.168.10.2 through .254. My second VM host would be 192.168.11.1; its VMs would range from 192.168.11.2 through 254, etc. Of course that leaves some big gaps within each range, but it does keep things organized (at least in my mind it does). I'm no network admin; do people segregate things this way?
There is another range of IP addresses 10.*.*.* for larger internal subnets. I would use that instead of 255.*.*.*
