You need to add static routes for the intranet network.
Example: (from a CMD box)
route add 172.23.45.0 mask 255.255.255.0 172.23.42.1 -p
172.23.45.0 is the network you want to reach.
172.23.42.1 is the gateway that will get you there.
-p to make it persistent, it will remain after you restart your computer.
I think your problem is that you have two default routes (0.0.0.0).
So I’m clear, your Internet connection is via the wireless interface (192.168.1.x/24) and your intranet is via the wired interface (172.23.42.x/24). Is that correct? I’m further assuming that your intranet exists entirely at 172.23.42.x/24 and that 172.23.45.x doesn’t actually exist. (Not sure where @Cesar got that from). Note: The ‘/24’ annotation is shorthand for a 24-bit netmask, or 255.255.255.0.
On the assumption that the above is accurate, you need to delete the default route for the intranet interface.
route delete 0.0.0.0 mask 255.255.255.0 172.23.42.1
The following route, from your routing table, takes care of getting intranet traffic to the right place:
172.23.42.0 255.255.255.0 On-link 172.23.42.164 276