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Windows Box behind Red shows "unknown Network"

PLilie

Hello everybody - I am new to the Sophos community and I could not find a solution to my problem in the existing posts. That might be an indication that I might be missing on something very basic.

In our office we have a SG135. Two SD-RED 20 devices are coupled to the UTM. 

The reds1 device is configured in Standard/Split and it works fine - a Windows Box behind the RED gets an IP from the Domain-Server behind the UTM. 

The reds2 is planned to be set up the same way but when I configure it identical to red1 and therefore in Standard/Split mode, the windows box behind the reds2 does not get an IP from the Domain-Server but indicates "Unknown network - no internet access". When the reds is configured to Transparent/Split (as shown above) it has internet access but not any access to the Network behind the UTM (and certainly no IP from the internal network).



I configured the interface to bridge both reds2 to the internal network:

I further switched DHCP-Relay to the internal DHCP server. 

The windows box behind reds2 is set to fetch its IP via DHCP.

I am at a loss at understanding why the Windows boxes behind the REDs behave so differently. I should mention that the routers through which the REDs connect are different brands but the REDs both show a stable tunnel to the UTM.

A first analysis of the logs did not show anything special - however, I might be looking up the wrong logs.

I would be thankful for any suggestions.



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  • FormerMember
    0 FormerMember

    Hi ,

    Thank you for reaching out to the Community! 

    In Transparent/Split mode, the UTM isn’t expected to manage the remote network. 

    Check out the following technical guide for more info: 

    Note: This technical guide also applies to the UTM.

    What is your use case for using Transparent/Split mode and not Standard/Split mode? 

    Thanks,

  • 0 in reply to FormerMember

    Hi Harsh,

    Thank you so much for your attention.

    I am aware of the different modes, however, I tried to explain in my previous post that the second RED was set to Transparent/Split because the windows box behind it does not have internet access if it is configured the same way as the first RED. I am aware of the fact that in this configruation it will not get an IP from the DHCP server behind the UTM. It is in that mode only for the box behind it to have internet access.

    If I switch it to the same mode as the first RED (Standard/Split) the windows box behind it does not get an address - in contrast to windows boxes behind the identically configured RED1. I do not understand why windows systems behind two identically configured REDs (both in Standard/Split) do not both receive IP from the Domain DHCP.

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