network IP address space seems odd

[Justinh]

Defining the IPv4 network seems discombobulated to me. Am I missing something in the firmware?
LAN - LAN IP lets you set the router's IP address and a subnet mask.
LAN - DHCP Server lets you set the IP pool start/end addresses, which may or may not be the usable address range.

There is not a straightforward way to say "this is the starting address and subnet mask".

So is the address range inferred by the LAN IP settings (knowing the router's address could be anything in the usable range of the subnet mask)?

 

[ColinTaylor]

There is not a straightforward way to say "this is the starting address and subnet mask".

Subnet ranges don't really work that way.

So is the address range inferred by the LAN IP settings (knowing the router's address could be anything in the usable range of the subnet mask)?

Yes.

Bear in mind this is a home router so the options are simplified for the target audience. It assumes that the router's own IP address will either be at the beginning of the IP range or the end.

 

[Justinh]

Subnet ranges don't really work that way.

? I tend to think this way: My network address is x.x.x.x, apply the mask, and that gives me my range. A subnet mask can't be applied to just any network address and derive the range, can it? E.g, a network address of 10.1.1.24 with a subnet mask of 225.225.225.224 is invalid, right? (.24 falls in the range for network address .0)

So I can't arbitrarily set a range of host addresses. I guess this is what allows the firmware to calculate the range for the given host address and mask. (I assume the router wouldn't allow host addresses outside of the range via DHCP or otherwise ...)

 

[ColinTaylor]

A subnet mask can't be applied to just any network address and derive the range, can it?

Yes, that's exactly how it works. But "225.225.225.224" is not a valid subnet mask value.

Play with this: https://jodies.de/ipcalc

(I assume the router wouldn't allow host addresses outside of the range via DHCP or otherwise ...)

Regarding dnsmasq, the only restriction is that the DHCP addresses it manages must be within the subnet of the relevant interface. So for example you might have a DHCP range of 192.168.1.30 to 192.168.1.254 and also have some static devices at 192.168.1.10 and 192.168.1.20.

 

[Justinh]

Yes, that's exactly how it works. But "225.225.225.224" is not a valid subnet mask value.

Play with this: https://jodies.de/ipcalc

I used that site. It confirms that that mask is valid and you can't randomly select a network address.

To be sure, subnet mask and netmask mean the same thing?

In my original post, I mistakenly said "starting address" when I was thinking "network address".

Thanks

 

[ColinTaylor]

I used that site. It confirms that that mask is valid and you can't randomly select a network address.

Err... You said "225.225.225.224" but now you've entered /27 which is "255.255.255.224".

So 10.1.1.24 with a netmask of /27 gives you:


So to your original question, any host address combined with its netmask will give you the subnet information.

To be sure, subnet mask and netmask mean the same thing?

Yes they are the same thing.