inheriting fib from an interface

[Eugene Grosbein]

On Mon, Jan 23, 2017 at 05:31:22PM -0800, Don Lewis wrote:

> Let's say that I have an application running on a server that is
> connected to the Internet via two different ISPs and is using IP
> addresses (ISP A:10.0.0.10 and ISP B:192.168.1.10) delegated by those
> two ISPs on it's two interfaces.  Responses to requests sent to
> 10.0.0.10 should be sent via ISP A, and responses to requests sent to
> 192.168.1.10 should be ISB B.
> 
> There are a couple of different ways that I can think of to do this:
> 
> 1) Put the server behind another FreeBSD box that uses policy-based
>  routing to forward the outbound packets to the desired ISP.  My
>  understanding is that this only works for packet forwarding and not
>  for locally generated packets.

Single command "ipfw add 2000 fwd $ispgw2 ip from $ip2 to any out xmit $isp1_iface"
works for locally generated packets too.

It "fixes" outgoing routing path for packets
from IP belonging to "non-default" ISP2 when default route points to ISP1.