Sipura SPA behind NAT
~~~~~~~~~~~~~~~~~~~~~
The Sipura had problems running behind nat with a netted address.
It would often loose incomming or outgoing audio. Putting the Sipura
on an external IP means that it can not benefit from firewall rules.
Giving it a piblic IP which is static natted seems to work well.
Here is a sample configuration that works with a FreeBSD gateway.
  

                    +---------------------------------------------+
                    |  Gateway Machine                            |
                    +---------------------------------------------+
                    |                                             |
               +--> |  a.b.c.e (Existing Addresses Usage)         |
The Internet --+    |                                             |
               +--> |  a.b.c.s (Static NAT to 192.168.0.Sipura)   |
                    |          Block tcp traffic with ipfw        |
                    |          Static NAT this IP to Internal IP  |
                    |                                             |
                    |                                             |
                    |  192.168.0.1                                |
                    +------+--------------------------------------+
                           |
                           |
        +------------------+------------------+-----------...
        |                  |                  |
192.168.0.Sipura    192.168.0.PC_1     192.168.0.PC_2


a.b.c.e = Public IP Address
a.b.c.s = Public IP Address for Sipura


/etc/firewall.rules
~~~~~~~~~~~~~~~~~~~
# 00100 Rule 1
# 00200 Rule 2
#
# Do not let any tcp traffic out from the Sipura to its Public IP (Outbound)
00300 add deny tcp from any to a.b.c.s
#
# 00400 Rule 4
# 00500 Rule 5
#
# Anything that is not blocked is diverted to natd
00600 add divert natd all from any to any via ed1
#
# 00700 Rule 7
# 00800 Rule 8
# etc


/etc/natd.conf
~~~~~~~~~~~~~~
# Rule 1
# Rule 2
# Sipura traffic sent/received via dedicated public address
redirect_address 192.168.0.Sipura to a.b.c.s
# Rule 4
# Rule 5