Simple gateway from compute using iptables from vgw1 to vhost0 on linux host

simple-gw-with-internet-access

This assumes a single net n1 with 1.1.1.0/24 and vgw1 interface. Can be extended to use a public net and vgw1 on the public net

    python /opt/contrail/utils/provision_vgw_interface.py  --oper create  --interface vgw1 --subnets 1.1.1.0/24 --routes 0.0.0.0/0 --vrf default-domain:admin:n1:n1

If you run into error running above script, instead of `import InstanceService` and `import ttypes` use

        `from contrail_vrouter_api.gen_py.instance_service import InstanceService, ttypes`

Now do `ifconfig` and verify `vgw1` is present

Using steps from http://www.revsys.com/writings/quicktips/nat.html
   /sbin/iptables -t nat -A POSTROUTING -o vhost0 -j MASQUERADE
   /sbin/iptables -A FORWARD -i vhost0 -o vgw1 -m state --state RELATED,ESTABLISHED -j ACCEPT
   /sbin/iptables -A FORWARD -i vgw1 -o vhost0 -j ACCEPT