When you say you can't get inbound calls to come in over the sync 
connection what do you mean. Do you mean that the calls go outbound over 
the 256/256 but come in over the 1024/256? If thats the case the problem 
is that your asterisk box is registering its self to your VoIP provider 
using the 1024/256 connection.

If the case is that only outbound calls are working and inbound calls 
don't you may need to open port 5060 to your asterisk box (if using SIP) 
and 4569 for IAX2 if you want to allow outside connections. It may also 
be good to add localnet=192.168.2.1/255.255.255.0(replacing with your 
subnet/mask of course) to your sip.conf to help Asterisk deal with the NAT.

Jonathan

Chris Bagnall wrote:
> At a particular site I have 2 m0n0 boxes each in front of independent ADSL
> connections (one is 1024/256, the other is 256/256). Aim is to use the 1mb
> line for general web access with the 256k synchronous one for VoIP traffic
> through an Asterisk server.
> 
> I've configured the m0n0 on the faster connection as the DHCP server and
> defined a static route to the VoIP gateway (a.b.c.d) with the gateway being
> the IP of the second m0n0 box on the synchronous connection.
> 
> This works perfectly for outbound calls (and they definitely come from the
> IP range of the sync connection), but I can't get inbound calls to come in
> over the sync connection. I've defined a 1:1 NAT mapping for it to its IP on
> the sync m0n0.
> 
> Do I perhaps need to modify the routing table on the asterisk box itself,
> and can anyone suggest what it should be modified to? I don't want to just
> change the default gateway to the second m0n0 box since all other web
> traffic (which will be to random addresses) would also be redirected over
> the VoIP ADSL, and that would be bad.
> 
> Any suggestions gratefully appreciated.
> 
> Regards,
> 
> Chris