Question Double NAT Subnetting question

Oct 11, 2019
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I have two routers Router A is connected to Public Internet with the 192.168.1.x/24 network and I have another router (Let call it Router B) that is connected to the LAN port of Router A .That has a static IP address of 192.168.1.8 so I can set it in Router A DMZ's zone to let everything pass down to router B. Router B original network address is 10.0.0.x/8 with a subnet mask of 255.0.0.0/8. For practice I created a different network of 10.0.0.0/29 which would give me six usable hosts 2^4=8-2=6 and would let me create 536870912 subnetworks each having six hosts in them. Well I applied the first subnetwork 10.0.0.0/29 and it worked awesome on Router B. I set the Router Address of 10.0.0.1 and the devices got addresses of 10.0.0.2 through 10.0.0.6 since 10.0.0.7 is used for broadcast address. Then I completely took out the 1st subnetwork and tried putting in the second subnetwork which goes from 10.0.0.8/29 to 10.0.0.15 I used the 10.0.0.9 for Router B new address and 10.0.0.10 through 10.0.0.14 for the hosts address. Since 10.0.0.15 is used for the broadcast address for this 2nd subnet I am confused why the second subnet(10.0.0.8/29) didn't work in my router since the first one did. At first I thought it could have been a subnet mask problem. Then I rule that out since they both use the same subnet mask of 255.255.255.248/29. I even double checked with IP subnet Calculator website to make sure I create the subnet mask correctly and all the address in the correct places . You can click on the link below this sentence to see the first subnetwork I create .https://www.calculator.net/ip-subnet-calculator.html?cclass=a&csubnet=29&cip=10.0.0.0&ct.... Also, if you keep scrolling all the way to bottom of the website you can see where the 10.0.0.8/29 is the second subnet which it shows should work. Again I wouldn't be at such a lost if I didn't already test the first subnet out and know that it works! I figured that it would be as simple as taking the old subnet out and putting the new subnetwork in. I know IP subnet Calculator.com is right with the information that it is showing me. When it says you can create 32 possible networks with 255.255.255.248/29 subnet mask. It should be as simple as taken out the first subnet is plugging in the second subnet but it not.
Thank you for reading this have a great day!
-Drake
 
It likely is a software restriction or bug. The device you are playing with should not really be called a router but that is what the big box consumer stores call them. A real router you could assign different subnets to different lan ports.
Not sure I have seen it where the software will not even let you assign a mask other than a /24. These are designed for home use and they figure you never need anything different. Some will not even accept subnets other than 192.168.x.x.

What you did should work but it is not something that is commonly done so nobody reported the bug and it was not corrected.

If the "router" supports it I would load third party firmware like dd-wrt. You then will get actual router abilities...even routing protocols although they have little use in a home network.
 
Reactions: drakestergroves
Oct 11, 2019
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Thank you so much for your reply! The router in question is a ASUS Router(I can't remember the exact model number off the top of my head) funny thing is I do have ddwrt firmware installed on it. Thank you for telling me that I was doing everything right!:) Maybe now I will just tried to figured out how to do router command using the ddwrt firmware. But man that still is strange that one subnet will work and the other one won't.
-Drake
 

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