Firewall rules - manage modem on external side?


This is my setup:
- internet to modem known as
- modem to Astaro Security Gateway PC on NIC known as (external)
- the internal side NIC of the ASG is
- my wireless DLink router is working as a switch and is plugged into the ASG and is known as
- my SBS 2008 server is and is also the DHCP server

The ASG DNS forwarders are specified as my two ISP DNS servers followed my by SBS box - is that right?

But my question for now is: how do I access my modem ( from my laptop for config purposes? Is the a packet filter rule I can write, or do I actually have to plug it into the modem?


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russell124Connect With a Mentor Commented:
You need to put the modem and external NIC on a different subnet than your internal LAN subnet.  Right now both sides of your firewall are configured to use the Subnet.

Assuming you are using a subnet mask, I would keep the subnet for your internal network, and use a subnet (Or whatever Number you like, as long as it isn't for your DMZ subnet.  Change the modem IP to and your external Astaro interface IP to

Then change the internal Astaro IP to so that it is the default gateway for your internal network.  If you have these subnets properly configured, the routing should be taken care of automatically, and you will be able to access the modem via it's new IP address of

Your DNS settings should be ok, I typically use my windows DNS server as the listed DNS forwarder,  and then set the windows DNS to use the ISP forwarders, just make sure to add a packet filter rule to allow the DNS traffic from the ISP servers to your SBS server.
warrenrapsonAuthor Commented:
Mate, that is fantastic!

Those are some of the best instructions i've read. Thank you thank you thank you!!! Exactly what I needed!

I've got more questions re firewalls, ports and DNS - if you like, check this out:

Thanks again,

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