Sounds like it could possibly be a NAT issue too.  Is your IP01 all on a local area network behind a firewall?  Is the IP04 operating in a flat lan or are you taking advantage of the Vlan option in the Switchfin firmware?

btw; the Vlan option is GREAT!

Using the vlan option will allow you to separate the voice and data traffic.

With Switchfin the IP0x can operate on a separate ip address for GUI connection and management but the actual VoIP connections and RTP voice packets can operate in their own ip address space.

For example; the IP0x can be GUI managed at 192.168.1.101 but the vlan setup allows you to establish a vlan id of 25 and operate all the voice in it's own network with the IP0x at 192.168.25.101.

Please note this only separates the ip addressed packets.  To be complete you still need to add quality of service measures with packet priority and make sure the voice packets take delivery priority over the non-voice packets in the LAN switches. You need better, fully managed, switches to be doing all this but there are a number of affordable small business switches available.  Cisco has a great 8 port model is you need a small one.

Bottom line is running both PC, Mac, Linux server and/or desktop LAN data on the same LAN, (flat LAN), with a telephony platform is not a good way to deploy VoIP as you will not guarantee the voice will not be broken up or disrupted by someone's youtube video.  :-) 

Separate the data packets and place priority on them.  Doing this will make sure your voice information is delivered the best it can to the end point devices.

Google can give you most all you need to know.  Start here: http://en.wikipedia.org/wiki/IEEE_P802.1p

Other comment;  the ready to go Vlan function is one of the differences you will see in the Switchvoice product and Switchfin GUI you do not see in other Asterisk management packages.  Asterisk is GREAT but Asterisk requires proper networking and management to be installed and operate with 100% reliability and high quality voice capabilities.

I have fixed the IP01 box by reflashing a newer firmware SNV 456 and resetting the configuration. Audio is good.
Thanks,

Please think about this:

IAX2 only uses 1 port for both call messaging and the voice traffic where SIP separates the call messaging and places the voice in a range of RTP ports.

If all the calling is internal on the LAN and not external to the Internet or private WAN then your router settings should not be needed.  Port forwarding in not needed when using IAX2 or SIP devices on an internal LAN.

I'm confused.  Are you trying to operate IAX2 and SIP devices outside the LAN where your IP01 is located?  Earlier in your post you mentioned "IP01 is on local lan behind router.".

With the IP04 internal you should be able to operate any device without any gateway settings.  All it would need to know is it's ip address, subnet mask and a configuration server if you use one and the specific SIP server / SIP account information.   Are you getting ip and setup information from your DHCP server and a TFTP or https server? Or are your phones static programmed?  Is your DHCP server also your router?

If you can you provide more details of how you are building your VoIP network i'm sure we can assist some.  If you do provide this make clear what else is on your network.  For example if you had a server for streaming video on the same LAN as your phones and do not use Qos and Vlan for VoIP devices it is a pretty good bet your voice quality will be real bad...

Sounds like a simple setup and you have things covered pretty good.  Any outside SIP audio issues are generally nat related but not getting devices registering correctly on the lan would be concerning.  I would make sure everything is 100% inside before messing with the outside. 

I mentioned rev. 437.  I am using 452 on all my units.  What rev are you using at this time?  Have you compiled the latest?

If you have no audio ( or one way audio ) over Nat connection, make sure that you have following set in your sip.conf

externip=111.57.149.111
localnet=192.168.1.0/255.255.255.0

Where externalip is the ip of your wan port on the router and localnet is the address of your local network.

If not set it and reboot.
That should help.