I am using GP-5.2.6 with split tunnel, When ever the tunnel configured DNS not resolving a hostname, The traffic is not falling back to local DNS server configured in physical adaptor. Actually this is not working in all 5.2.x series.
But the same scenario working in GP-5.1.8(5.1.x). Palo Alto has introduce split-DNS feature from 5.2 series, Is it anything related with this issue.
You can test it on test users as it could be related for domains that are added to not enter the split tunnel:
Also see this option "Resolve All FQDNs Using DNS Servers Assigned by the Tunnel (Windows Only)" as it can also be related to your issue to test changing it for couple of test users that you made specific portal app config to be assigned based on AD user/group:
if needed upgrade to the latest globalprotect version.
I already Did, "Resolve All FQDNs Using DNS Servers Assigned by the Tunnel (Windows Only)" without this option in GP 5.1.x the DNS fall back to local DNS, But in 5.2.x it is not. But I enable "Resolve All FQDNs Using DNS Servers Assigned by the Tunnel (Windows Only)". It is working fine.
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