You can use DynamicForward ssh option, like this:
ssh -o DynamicForward=localhost:6661 yourserver
This way ssh client will listen on 6661 port on localhost for incoming connections. It implements SOCKS protocol so you can configure your Firefox or any other web browser to use this as a HTTP proxy server by using localhost:6661 address. This way all the HTTP requests made by Firefox will be actually made from your remote server so you an use 192.168.X.X addresses.
The shorer version of this is -D option which does the same:
ssh -D localhost:6661 yourserver
Saving yourself typing
You can also configure this option in .ssh/config file to save yourself typing if you want to enable this each time you connect to this host. Here's example:
host myhost
Hostname <yourvpnaddress>
DynamicForward localhost:6661
user <someuser>
Now, all you have to do is to run:
ssh myhost
and it will be equivalent to:
ssh -o DynamicForward=localhost:6661 -l <someuser> <yourvpnaddress>
Using proxy only for 192.168.X.X
If you want to only connect through this proxy when using 192.168.X.X addresses, you may use FoxyProxy Firefox extension (or something similar). It let you specify the list of proxy addresses associated only to specified URLs.
Using this proxy for other application
Some applications does not support SOCKS protocol so they can not be configured to use this method. Fortunately, there is solutions for this and it's called tsocks. It works as a wrapper converting all normal socket operations that application uses to the SOCKS request on the fly using LD_PRELOAD technique. It won't work for all the applications but it should for most. An alternative to tsocks is dante's socksify wrapper which also allows resolution of hostnames on the remote side.
