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Unable to connect to internal web servers through web proxy

Whenever an internal client device tries to access one of our internally hosted public web servers, the page is blocked by the UTM Firewall with the following message:

08:21:40 WebAdmin connection attempt HTTP  
*.*.*.120 : 46760
*.*.*.120 : 443
 
[SYN] len=60 ttl=64 tos=0x00 srcmac=00:00:00:00:00:00
  1.  *.*.*.120 in the logs is the public IP address of the web server being accessed.

The "WebAdmin connection attempt" error is particularly weird, because our WebAdmin console is not available on that interface, IP, or port.

Clients on the Internet, from outside of our network, are able to access the sites successfully. It is only clients using the UTM proxy being blocked.

We are using 3 Sophos UTM components:

1. Web Filter - Our clients all access the internet through the Sophos proxy server in Standard mode.

2. Firewall - All of our global IPs are on Sophos UTM Interfaces protected by the firewall.

3. Web Application Firewall - Our publicly hosted web servers are configured behind this.

Sophos support told me to use the browser settings to proxy bypass. This doesn't work, and frankly doesn't make any sense to me as a solution. The client would still be routed in and out of the same interfaces regardless.

One potential solution is split DNS. Unfortunately the internal web server is on a non-standard port, so this is less than ideal for our clients.

Any assistance would be very appreciated! I've seen this sort of problem posted many times on the Sophos forums, but haven't found any posts with a solution.



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  • Hi, Austin, and welcome to the UTM Community!

    Your best bet is to set up split DNS and clone the Virtual Servers to attach the clones to the Internal interface.

    EDIT 2016-11-02: Thanks to Derek below, I was reminded that you need to make sure your client browsers skip the Proxy and go directly to the Virtual Servers.  That's the Transparent Mode Skiplist for Profiles using Transparent mode and, for Standard mode Profiles, in a PAC file or GPO to configure 'LAN Settings' in Windows clients.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • Thanks Bob,

    I was hoping there was a solution other than split DNS, as the web server is on a non-standard port internally.

    There is no way to prevent the Sophos firewall from blocking internal traffic in this scenario?

Reply Children
  • Split DNS to aim the FQDNs at Additional Addresses on the Internal interface. You just duplicate the structure that you have defined on the External interface.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA