Overlapping address error in Packet Tracer-Possible subnet error

Question

I am working on my hands on final exam for Networking Fundamentals. I have accomplished everything except for putting the 4 devices on two separate subnets. These are my subnet calculations: Given address:192.168.10.0/24

192.168.10.0[1-126 hosts] [127 broadcast] 192.168.10.128[129-254] [255]

I know the calculations themselves are correct because I checked my work with a subnet calculator. All devices accepted their addresses with their assigned subnet mask of either 255.255.255.0 or 255.255.255.128. However after assigning the appropriate addressing on my router g0/0 port (subnet A) I get an overlapping address error when trying to assign g0/1 (subnet B) the appropriate address. Is something not configured correctly with the router, or did I subnet wrong? Any help would be greatly appreciated as I have become very desperate. Thank you. P.S. I also encounter the same problem when trying to assign ipv6 addresses to the router ( 2001:DB8:ACAD::/64 and I try the addresses 2001:DB8:ACAD::1 and 2001:DB8:ACAD::2 respectively)

Solution

A /24 is equivalent to a netmask of 255.255.255.0, so you can't stuff two networks inside the 192.168.10.0/24. You should tell the router that it has 192.168.10.0/25 (a netmask of 255.255.255.128) for the first network, and 192.168.10.128/25 for the second network.

Comments

[ganesh]

Can you clarify the part where you say "subnet mask of either 255.255.255.0"? Also, does this describe your setup? i.stack.imgur.com/zuW3Y.png

[ganesh]

Upvoted because you are technically right and because I strongly suspect that this is what the OP is trying to do.