To begin with, running natd on the host system should not be necessary. Both your primary and alias (host and jail, respectively) IP addresses are RFC 1918 address space, so I'm presuming that you are behind a home router/NAT device already anyway. Which is a long way of saying: if your internet connection is working on the host system, you should be able to get it working similarly on the jailed system.
NB a couple points:
- You will need to add nameservers to /etc/resolv.conf within your jail.
- You can not ping from within a jail. Instead use nc or nmap (or the like) for testing connectivity. edit: sorry -- I see you've enabled raw sockets. So you should be able to use ping to test connectivity.
Hope this helps.