OpenVPN client for access via IP Alias network

[P-Chan]

I'm wanting to create a secondary network (10.11.12.1/24 is the normal network, a subinterface (IP Alias) for 10.10.10.1/24) which exclusive access via an OpenVPN client connection.  How would I go about doing this?  I'm guessing I'd want to disable the automatic gateway redirect from OpenVPN and use NAT rules?  If this is the case, I can figure out the disabling of the automatic default route (I think it's no-dfl-gw or something like that, I can look it up), but I'm not sure where/how to configure IPtables for this.  Also, my IP Alias I have set I cannot ping on my local network from machines manually configured to being on that network, but I'm not sure what (if anything) I did wrong (for now I'm assuming it's not enabled for pings).