Howto setup one machine for specific ip pipe?

[sean darcy <seandarcy2@gmail.com>]

I have an asterisk voip server in the local network. I have two outgoing 
connections, a large verizon pipe, and small, low latency pipe from 
broadview. I'd like traffic generally to use the verizon pipe, but 
traffic from the voip server should use the low latency broadview pipe.

I've set up table 128:


## eth0 is static to broadview
ETH0_IP_GATEWAY=xx.yy.zz.ww
ETH0_IP_ADDR=xxx.yy.zz.ww1
ip rule delete from $ETH0_IP_ADDR/32 table 128 priority 128
ip rule add    from $ETH0_IP_ADDR/32 table 128 priority 128
## this is the route through broadview gateway ip
ip route add default via $ETH0_IP_GATEWAY table 128

ip rule add    fwmark 0x1 table 128 prio 126

ip rule add    fwmark 0x2 table 128 prio 127

and then set-mark 0x1 to all packets from the voip server:

$IPT -t mangle -A PREROUTING -i eth1 \
   -s $AST_IP_ADDR -j MARK --set-mark 0x1


But the asterisk server can't access the internet. I assume the problem 
is that iptable server isn't NAT'ing the voip server. That is, it routes 
the packet out through the broadview pipe, but doesn't send any of the 
responses back to the asterisk server.

Any help appreciated.

sean