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Robert Biehl
Beginner

Trying to block all traffic, but allow a one way data transfer.

Hello all,

I am trying to connect a Control network that can not have access to the Internet, or any other network for that matter, to my Admin network so that I can retrieve trend data about the plant that goes into a database. Right now the process is print information, hand jam into excel spreadsheet, print again, and hand jam into another excel spreadsheet on the other network. Reports are printed automatically once a day, but would like a simplified way of getting data from one network to the other without having to re-enter data several times. Current policies stipulate no USB drives connected to Control systems. Even if we could loosen that, personnel needed to transfer data is not available and going to each individual machine would take more time than current system.

Now that background is laid, I have two 2911 ISR routers with EIGRP configured, each with a 4 port EHWIC card. The 3 L3 ports on the router are setup as follows: interface G0/1 to the internet, interface G0/2 to a wireless  back haul, and interface G0/0 for IT network. I then have 3 VLANs setup on the EHWICs for our Admin network. We will move the IT network to a VLAN on the remaining EHWIC port and connect the two 2911's through the G0/0 interface. I am going to have one computer on my Administration network dedicated to receiving the information and have a program that will take that data and import it to a database. I need to allow only that computer to receive traffic from the Control network and I need no traffic to flow back into the Control network. In other words I will transmit data from the control network to the admin computer using one protocol (TFTP more than likely) and block any other traffic coming out of and going into the Control network.

I am hoping this can be achieved with an ACL, but fear that because traffic is by default bidirectional, any attempt to block a received packet will drop the connection.

Any insight is welcome.

1 REPLY 1
Elton Babcock
Beginner

I am a fan of zone based firewall myself. Gives you a lot of control and allows for stateful traffic to pass pack through.

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