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UTM interface to connect to on-the-premises router (behind the firewall) with a WAN IP

B.R.O.

On this diagram we have several objects to look at

WAN IP = 12.12.12.35

LAN IP of UTM = 8.8.8.8

WAN IP of Router behind firewall = 12.12.12.36

LAN IP of Router behind firewall 8.8.8.4

 

 

How would you configure Port 4 to plug a cable from the UTM to the WAN Port of the Router? 

 

I plan to configure interface X4 = 12.12.12.36/32 proxy-arp enabled

 

now granted if the firewall rules are correct to allow full ip from 12.12.12.36 to get out through the internet to connect to defined router (10.10.10.10)

I think the Utm will see traffic from defined router (10.10.10.10) from any source (port 2 wan 12.12.12.35), permit it to pass to port 4 12.12.12.36.  Transparent traffic ???

In theory this should work right?  

If the router because of vpn tunnel policies didn't need the wan ip configured a nat rule would be sufficient.  

Other alternative create dmz ip for the interface and have the router's wan ip changed to avoid messing up the routing table.



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    I would change the WAN Interface definition to "Ethernet Bridge" and add NIC X4 to it.  Try first without Proxy ARP, but I bet you will need it.

    The alternative is to create a DMZ with a public subnet and to ask your ISP to route traffic to it via 12.12.12.35.  This requires no bridge and no Proxy ARP, but uses a separate Interface definition with an IP in the public subnet of the public DMZ.

    Both approaches require a firewall rule.

    Cheers - Bob
    PS Using the IPs of the Google name servers created cognitive dissonance when I first tried to understand what you wanted to accomplish.  I guessed that you meant IPs in 10.10.10.0/24, but I admit I'm still not clear.

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
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    MediaSoft, Inc. USA
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