Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: OpenVPN 2.4.7 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Feb 20 2019 Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: library versions: OpenSSL 1.1.1d 10 Sep 2019, LZO 2.10 Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: Outgoing Static Key Encryption: Cipher 'BF-CBC' initialized with 128 bit key Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: WARNING: INSECURE cipher with block size less than 128 bit (64 bit). This allows attacks like SWEET32. Mitigate by using a --cipher with a larger block size (e.g. AES-256-CBC). Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: Outgoing Static Key Encryption: Using 160 bit message hash 'SHA1' for HMAC authentication Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: Incoming Static Key Encryption: Cipher 'BF-CBC' initialized with 128 bit key Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: WARNING: INSECURE cipher with block size less than 128 bit (64 bit). This allows attacks like SWEET32. Mitigate by using a --cipher with a larger block size (e.g. AES-256-CBC). Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: Incoming Static Key Encryption: Using 160 bit message hash 'SHA1' for HMAC authentication Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: RESOLVE: Cannot resolve host address: 172.18.202.10:1195 (Address family for hostname not supported) Apr 19 17:55:47 LR2 openvpn-vtun1[8521]: Exiting due to fatal error
Bug introduced here https://github.com/vyos/vyos-1x/commit/bb9f99853c723c5100c3fffbc592ba79f3abebfe#diff-b706c6ec71f1314215d25bf1fcec7c08R21
As soon as udp6 is replaced with udp all works nicely again.