You could simplify that by opening up your netmask to span 192.168.0 .. 192.168.2 ...
I.E: a network mask of 255.255.252.0 will give you a /22 network
(192.168.0.0 .. 192.168.3.255)
A /23 network would not encompass any of the 192.168.2.x sub-net.
Now that gives you a /22 bit network instead of the /24 bit network, which encompasses all of the address you are using in the posts.
No nat or masquerade required on the local network, only at the point which you exit the local network to the world.
Since you have more than one physical network - -
Then enable the arp proxy service as shown at the top of my post.
Three more hints if you want "simple" -
* Your ubuntu install has the ip set of utilities - stop using the many decades old ones you are using.
* Stop trying do the setup in the /etc/network/interfaces file (used for ifup and ifdown) - just script it in bash.
* Since Network manager tries to "manage" the same file, put an end to that also by adding:
Code:
[ifupdown]
managed=false
To the /etc/NetworkManager/NetworkManager.conf file.
Next question -
Where is the physical connection to the world being made?
On the machine running ddwrt ?
If so, use that machines IP address as the "Gateway" address on everything else.
No special entries under ddwrt - with the /22 network, everything will "just work".
If you really want "simple" - - then stop trying to (mis-)use all of the complicated stuff.