Same issue here. DNS is going to the router-assigned DNS servers, not the VPN-assigned servers.
Specific example, with confidential info replaced:
C:\Users\*****>ipconfig /all
Windows IP Configuration
Host Name . . . . . . . . . . . . : *****
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : lan
Ethernet adapter Ethernet:
Connection-specific DNS Suffix . : lan
Description . . . . . . . . . . . : Intel(R) Ethernet Connection (7) I219-LM
Physical Address. . . . . . . . . : <MAC address>
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::3c38:d255:d9cb:8968%17(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.86.41(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Monday, October 4, 2021 6:39:38 PM
Lease Expires . . . . . . . . . . : Thursday, October 7, 2021 3:45:10 AM
Default Gateway . . . . . . . . . : 192.168.86.1
DHCP Server . . . . . . . . . . . : 192.168.86.1
DHCPv6 IAID . . . . . . . . . . . : 115627240
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-25-6F-DB-E4-E4-54-E8-74-6F-FD
DNS Servers . . . . . . . . . . . : 192.168.86.1
NetBIOS over Tcpip. . . . . . . . : Enabled
PPP adapter <The VPN connection name>:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : <The VPN connection name>
Physical Address. . . . . . . . . :
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : <DHCP address assigned by the MX100>(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . :
DNS Servers . . . . . . . . . . . : <Internal DNS server 1>
<Internal DNS server 2>
NetBIOS over Tcpip. . . . . . . . : Enabled
C:\Users\*****>nslookup <website>.com
Server: UnKnown
Address: 192.168.86.1
Non-authoritative answer:
Name: <website>.com
Address: <public address>
C:\Users\*****>ping <Internal DNS server 1>
Pinging <Internal DNS server 1> with 32 bytes of data:
Reply from <Internal DNS server 1>: bytes=32 time=4ms TTL=125
Reply from <Internal DNS server 1>: bytes=32 time=3ms TTL=125
Reply from <Internal DNS server 1>: bytes=32 time=16ms TTL=125
Reply from <Internal DNS server 1>: bytes=32 time=4ms TTL=125
Ping statistics for <Internal DNS server 1>:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 3ms, Maximum = 16ms, Average = 6ms