Networking :: LAN Must Use ISP 2 To Go To Internet And VOiP Server Must Use ISP1?

I have Ubuntu 10.10 server gateway:

Code:
_______________________________
| ISP1 |<---->|ADSL modem, internal IP 192.168.1.1 |<------->|eth0 IP 192.168.1.10 |
|ubuntu server |
| ISP2 |<--------------------------------------------------->|wimax0,

[code]....

My goal is LAN must use ISP 2 to go to Internet and VOiP server must use ISP1. So, I write some iptables rules:

Code:

#!/bin/sh
#
IPT="/sbin/iptables"
# Internet Interface

[code]....

But there is problem: packets from DMZ network are not natting or may be something else wrong.Also my routing table:

Code:

# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 199 0 0 eth0

[code]....