我只能使用 IPv6 而不是 IPv4 连接到 OpenVPN 服务器

我在 Synology Router 上设置了 OpenVPN 服务器，但无法让 IPv4 和 IPv6 连接正常工作。最初，我在弄清楚这一点时非常头疼，但我已将其缩小到这一点：我可以通过它的 IPv6 地址成功连接到我的 OpenVPN 服务器，但每次仅通过 IPv4 地址连接都会失败。

我正在通过使用 DDNS 设置的域名进行连接。如果我手动将记录设置为仅 IPv4 地址，它当然会失败。一旦我更新 IPv6 记录，它就会正常工作。

我已经在几个不同的客户端和网络上对此进行了测试，以确保它不是我的客户端所在的网络。

这是我的服务器配置： 服务器配置

和客户端配置文件：

dev tun
tls-client

remote my.domain.com 1194

redirect-gateway def1


pull

proto udp

script-security 2


reneg-sec 0

auth SHA1

cipher AES-128-CBC

auth-user-pass


key-direction 1

comp-lzo
explicit-exit-notify
<ca>

-----BEGIN CERTIFICATE-----

-----END CERTIFICATE-----
</ca>

<tls-auth>

-----BEGIN OpenVPN Static key V1-----

-----END OpenVPN Static key V1-----
</tls-auth>

这是客户端连接日志文件，已针对个人信息进行了编辑：

5/20/2020, 1:03:10 AM OpenVPN core 3.git::15c71c44 win x86_64 64-bit PT_PROXY built on Feb 19 2020 17:36:01
⏎5/20/2020, 1:03:10 AM Frame=512/2048/512 mssfix-ctrl=1250
⏎5/20/2020, 1:03:10 AM UNUSED OPTIONS
1 [tls-client] 
4 [pull] 
6 [script-security] [2] 
13 [explicit-exit-notify] 
⏎5/20/2020, 1:03:10 AM EVENT: RESOLVE 
⏎5/20/2020, 1:03:10 AM EVENT: WAIT 
⏎5/20/2020, 1:03:10 AM Contacting 104.232.115.21:1194 via UDP
⏎5/20/2020, 1:03:10 AM Connecting to [my.domain.com]:1194 (x.x.x.x) via UDPv4
⏎5/20/2020, 1:03:20 AM Server poll timeout, trying next remote entry...
⏎5/20/2020, 1:03:20 AM EVENT: RECONNECTING
⏎5/20/2020, 1:03:20 AM EVENT: RESOLVE
⏎5/20/2020, 1:03:20 AM Contacting x.x.x.x:1194 via UDP
⏎5/20/2020, 1:03:20 AM Connecting to [my.domain.com]:1194 (x.x.x.x) via UDPv4
⏎5/20/2020, 1:03:20 AM EVENT: WAIT 
⏎5/20/2020, 1:03:30 AM Server poll timeout, trying next remote entry...

5 次尝试失败，直到超时：

⏎5/20/2020, 1:04:10 AM EVENT: CONNECTION_TIMEOUT
⏎5/20/2020, 1:04:10 AM EVENT: DISCONNECTED

现在尝试 IPv6 地址

⏎5/20/2020, 1:04:46 AM OpenVPN core 3.git::15c71c44 win x86_64 64-bit PT_PROXY built on Feb 19 2020 17:36:01
⏎5/20/2020, 1:04:46 AM Frame=512/2048/512 mssfix-ctrl=1250
⏎5/20/2020, 1:04:46 AM UNUSED OPTIONS
1 [tls-client] 
4 [pull] 
6 [script-security] [2] 
13 [explicit-exit-notify] 
⏎5/20/2020, 1:04:46 AM EVENT: RESOLVE
⏎5/20/2020, 1:04:46 AM EVENT: WAIT
⏎5/20/2020, 1:04:46 AM Contacting x.x.x.x:1194 via UDP
⏎5/20/2020, 1:04:46 AM Connecting to [my.domain.com]:1194 (x.x.x.x) via UDPv4
⏎5/20/2020, 1:04:56 AM Server poll timeout, trying next remote entry...
⏎5/20/2020, 1:04:56 AM EVENT: RECONNECTING
⏎5/20/2020, 1:04:56 AM EVENT: RESOLVE
⏎5/20/2020, 1:04:56 AM EVENT: WAIT
⏎5/20/2020, 1:04:56 AM Contacting 104.232.115.21:1194 via UDP
⏎5/20/2020, 1:04:56 AM Connecting to [my.domain.com]:1194 (x.x.x.x) via UDPv4
⏎5/20/2020, 1:05:06 AM Server poll timeout, trying next remote entry...
⏎5/20/2020, 1:05:06 AM EVENT: RECONNECTING
⏎5/20/2020, 1:05:06 AM EVENT: RESOLVE
⏎5/20/2020, 1:05:06 AM EVENT: WAIT
⏎5/20/2020, 1:05:06 AM Contacting [xxxx::xxxx]:1194 via UDP
⏎5/20/2020, 1:05:06 AM Connecting to [my.domain.com]:1194 (xxxx::xxxx) via UDPv6
⏎5/20/2020, 1:05:06 AM EVENT: CONNECTING
⏎5/20/2020, 1:05:06 AM Tunnel Options:V4,dev-type tun,link-mtu 1558,tun-mtu 1500,proto UDPv4,comp-lzo,keydir 1,cipher AES-128-CBC,auth SHA1,keysize 128,tls-auth,key-method 2,tls-client
⏎5/20/2020, 1:05:06 AM Creds: Username/Password
⏎5/20/2020, 1:05:06 AM Peer Info:
IV_GUI_VER=OCmacOS_3.1.2-572
IV_VER=3.git::15c71c44
IV_PLAT=win
IV_NCP=2
IV_TCPNL=1
IV_PROTO=2
IV_LZO_STUB=1
IV_COMP_STUB=1
IV_COMP_STUBv2=1

⏎5/20/2020, 1:05:06 AM VERIFY OK : depth=1
Certificate Information

⏎5/20/2020, 1:05:06 AM VERIFY OK : depth=0
Certificate Information

⏎5/20/2020, 1:05:08 AM SSL Handshake: TLSv1.2/TLS-DHE-RSA-WITH-AES-256-GCM-SHA384
⏎5/20/2020, 1:05:08 AM Session is ACTIVE
⏎5/20/2020, 1:05:08 AM Sending PUSH_REQUEST to server...
⏎5/20/2020, 1:05:08 AM EVENT: GET_CONFIG 
⏎5/20/2020, 1:05:09 AM EVENT: DISCONNECTED

如您所见，使用 IPv6 地址时，它可以正常连接。但是当尝试连接 IPv4 地址时，它每次都会失败。这与我的 ISP 阻止某些 UDP 数据包有关吗？我很好奇为什么它只适用于 IPv6。