Confused by subnetting

[dmlaero]

I've done some reading/research trying to understand subnetting, but I'm still thoroughly confused. I'm just playing around with some basics to try to understand things, but still having trouble. For example, I was experimenting just using my PC, router, and cable modem as my "network." If I set my router IP to 192.168.1.1 with a 255.255.255.0 subnet mask, I can log in to the cable modem GUI at 192.168.100.1. However, if I change the router IP to 192.168.0.1 with a 255.255.252.0 subnet mask then I can no longer login to the cable modem GUI at 192.168.100.1. This makes no sense to me as 192.168.100.1 is not in the address pool of either subnet configuration so I don't know why one will connect and the other won't. Any simple explanation for this or good resources to help me understand?

 

[eibgrad]

Did you reboot everything after the change (PC, router, and modem)?

 

[dmlaero]

Did you reboot everything after the change (PC, router, and modem)?

No, I did not reboot anything. Is that required when changing the configuration? Should I theoretically be able to connect with 192.168.100.1 using either config?

 

[eibgrad]

Based on your description, I find no reason it shouldn't have worked. But given it was a configuration change, and apparently didn't work, it would be prudent to reboot everything first before wasting time trying to diagnose it further.

 

[dmlaero]

Based on your description, I find no reason it shouldn't have worked. But given it was a configuration change, and apparently didn't work, it would be prudent to reboot everything first before wasting time trying to diagnose it further.

I'll have to give that a shot once the family is offline and I can experiment a bit.

 

[itpp20]

The cable modem is behind the router, the subnet+mask will inform the router what it can handle itself and if not to push it out the door (to the modem and beyond), I think (not verified) that 0.1 with a 252.0(/22) mask includes 100.1 and hence is not getting pushed out the door (and not reaching the modem).

 

[eibgrad]

192.168.0.1/255.255.252.0 (or 192.168.0.1/22) does NOT include 192.168.100.1. That IP range contains everything from 192.168.0.0 through 192.168.3.255 (1024 hosts (1022 usable)). Any CIDR to IP Range calculator on the 'net will confirm this (there are many).

CIDR to IP Addresses Ranges Converter, Subnet, Mask, Broadcast, Network Address

CIDR to IP ranges Converter. Convert from CIDR to IP, subnet mask, network, broadcast addresses and total count.

www.ipconvertertools.com

 

[dmlaero]

192.168.0.1/255.255.252.0 (or 192.168.0.1/22) does NOT include 192.168.100.1. That IP range contains everything from 192.168.0.0 through 192.168.3.255 (1024 hosts (1022 usable)). Any CIDR to IP Range calculator on the 'net will confirm this (there are many).

CIDR to IP Addresses Ranges Converter, Subnet, Mask, Broadcast, Network Address

CIDR to IP ranges Converter. Convert from CIDR to IP, subnet mask, network, broadcast addresses and total count.

www.ipconvertertools.com

Yes, that is the same conclusion I came to after using one of the online calculators. Unfortunately, I haven't had an opportunity to do anymore experimentation yet. Too many teen users in my household