NATD will not start with punch_fw option

[SKU]

Greetings,

I am working with 2 different machines that refuse to start natd with the punch_fw option.   As of this morning, one machine is up to date 4.8 stable and the other has sources from 4.11.03.

The problem is very hard to figure out.   When starting natd like:

/sbin/natd -n sis0 -punch_fw 100:4

It simply does not fork to the background and start processing packets.  Top shows natd with a state of run but is using 90%+ processor.  Also, it refuses to move packets.

If I start natd like this:

/sbin/natd -n sis0

The above works fine.  It immediately forks to the background and gives the message:

Aug 12 20:43:23 natd[432]: Aliasing to 10.0.250.173, mtu 1500 bytes

I have tried blowing away my source tree 3 times and have been working on this silly issue since sunday.   Also, this has happened in the past but I have no idea how I fixed it.

So my question is, does anybody have a cluestick that they can hit me with a couple of times?   It's bizarre that punch_fw does not work.   I have tried every option that I can think of including -dynamic -s -m etc but punch_fw is the deal breaker each time.

Thanks in advance,

SKU