DNS Server in DHCP options keeps changing to Sophos IP

Question

Hi All... 
 Customer has XG135 (SFOS 19.5.3 MR-3-Build652), Sophos is the main DHCP server for the network, for the last few months we have been battling with a strange issue. 
 Sophos LAN IP is 172.16.0.10 
 Internal Microsoft DNS server 172.16.0.1. 
 DHCP on the Sophos is configured to use 172.16.0.1 for the DNS, Randomly the Sophos will change the DNS server to itself (172.16.0.10) - Causing DHCP clients to get 172.16.0.10 DNS which then causes issues with internal DNS resolution. 
 Multiple support tickets opened with support- the keep wanting to read logs and to tell them when it happens- no actual help to resolve this. 
 Customer does have multiple static reservations configured on Sophos DHCP. 
 Anyone had this issue before or have any suggestions?

Vishal_R · Accepted Answer

Hi Rog163 Thank you for sharing the Support ticket ID details.

Based on shared information your reported issue situation matches the below ID:

NC-131365 - DNS server IP address in DHCP server configuration is changed unexpectedly at XG Webadmin sometimes

The fix for the above issue is marked with 20.0.2 MR-2, I have also added a note over the case for the case owner's reference to drive it further.

Bharat J · Answer

Hi Roger Da Camara 
 Try to set DNS1 as 172.16.0.1 on DNS settings as below and then tick mark Use device's DNS settings under DHCP or untick Use device's DNS settings and set your DNS IP on DHCP server might help to fix the issue.

Regards

DNS Server in DHCP options keeps changing to Sophos IP

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