Solution #:00007694
Scope: Web Filter Version 7 or above.
When setting your DNS for Primary or secondary, How to set on a 1010/1011 box with multiple NICs.
Answer:
Only set Primary DNS for LAN/WAN1 to use this DNS
Set Secondary DNS for LAN/WAN2 to use as needed.
Considering these 2 networks are not able to traverse it cannot reach the other subnet possibly to resolve the other DNS.
Setting both DNS may cause traffic issues to then try using another path to DNS if LAN/WAN2 is also used or even filled in.
Link to This Page:
https://campus.barracuda.com/solution/50160000000WKB9AAO