Connection to VPN adds unreachable IPv6 address
Posted: Fri Sep 28, 2018 9:13 am
On Windows 10 some applications fail to connect to public website when VPN is connected.
After some digging I found out that nslookup returns 3 IPv4 and 3 IPv6 addresses for the host. These addresses are the same before and after connection to VPN.
For some applications situation is a bit different. When VPN is NOT connected then getaddrinfo() windows function returns 3 IPv4 addresses. These addresses work fine and connections can be made.
After connection to VPN the same call to getaddrinfo() returns 3 IPv6 and 3 IPv4 addresses. In this case IPv6 addresses are unreachable but they are at the start of the list so any attempt to connect now fails.
I noticed that Outlook had the same connection problem if it was started after VPN connection was made.
So why connection to VPN adds 3 IPv6 addresses for the host? How can I get rid of them?
After some digging I found out that nslookup returns 3 IPv4 and 3 IPv6 addresses for the host. These addresses are the same before and after connection to VPN.
For some applications situation is a bit different. When VPN is NOT connected then getaddrinfo() windows function returns 3 IPv4 addresses. These addresses work fine and connections can be made.
After connection to VPN the same call to getaddrinfo() returns 3 IPv6 and 3 IPv4 addresses. In this case IPv6 addresses are unreachable but they are at the start of the list so any attempt to connect now fails.
I noticed that Outlook had the same connection problem if it was started after VPN connection was made.
So why connection to VPN adds 3 IPv6 addresses for the host? How can I get rid of them?