Ubuntu 22.04连接OpenVPN客户端后网络完全中断问题求助

大家好，我把能谷歌的内容都搜遍了，还是没能解决问题，现在把我的问题尽量简化一下，希望能得到大家的帮助：

问题现象 #

连接VPN之后，我的网络直接“完全崩溃”——既ping不通VPN服务器（10.8.0.1），也ping不通Google DNS（8.8.8.8），甚至连我自己的互联网网关（178.xxx.xxx.xxx）也无法访问。但只要关闭VPN客户端，所有网络功能就立刻恢复正常。

连接VPN前后的路由表 #

连接前（网络正常） #

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         178.xxx.xxx.xxx 0.0.0.0         UG    0      0        0 enp5s0
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0

连接后（网络中断） #

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.8.0.1        128.0.0.0       UG    0      0        0 tun0
0.0.0.0         178.xxx.xxx.xxx 0.0.0.0         UG    0      0        0 enp5s0
10.8.0.0        0.0.0.0         255.255.255.0   U     0      0        0 tun0
128.0.0.0       10.8.0.1        128.0.0.0       UG    0      0        0 tun0
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0

ip route show 输出 #

连接前（网络正常） #

ip route show
default via 178.xxx.xxx.xxx dev enp5s0 proto static onlink
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown

连接后（网络中断） #

ip route show
0.0.0.0/1 via 10.8.0.1 dev tun0
default via 178.xxx.xxx.xxx dev enp5s0 proto static onlink
10.8.0.0/24 dev tun0 proto kernel scope link src 10.8.0.2
128.0.0.0/1 via 10.8.0.1 dev tun0
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown

互联网接口enp5s0的ifconfig输出 #

ifconfig enp5s0
enp5s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet 178.xxx.xxx.xxx  netmask 255.255.255.255  broadcast 0.0.0.0
inet6 2a01:xxx:xxx:xxx::2  prefixlen 64  scopeid 0x0<global>
inet6 fe80::xxx:xxx:xxx:c860  prefixlen 64  scopeid 0x20<link>
ether a0:36:bc:ca:c8:60  txqueuelen 1000  (Ethernet)
RX packets 110506  bytes 18354128 (18.3 MB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 117994  bytes 17466604 (17.4 MB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
device memory 0x81c00000-81cfffff

VPN客户端日志（连接成功后因网络问题断开） #

May 30 16:54:35 client openvpn3-service-logger[20691]: {tag:5238658794065795403} Adding IP Adress 10.8.0.2/24 gw 10.8.0.1 ipv6: no
May 30 16:54:35 client openvpn3-service-logger[20691]: {tag:5238658794065795403} Setting remote IP address to 195.xxx.xxx.xxx ipv6: no
May 30 16:54:35 client openvpn3-service-logger[20691]: {tag:17752863769272376516} Connected: 195.xxx.xxx.xxx:1194 (195.xxx.xxx.xxx) via /TCPv4 on tun/10.8.0.2/ gw=[10.8.0.1/]

VPN服务器日志（对应连接情况） #

May 30 16:54:34 server ovpn-server[62795]: 178.xxx.xxx.xxx:41434 [client] Peer Connection Initiated with [AF_INET]178.xxx.xxx.xxx:41434
May 30 16:54:34 server ovpn-server[62795]: client/178.xxx.xxx.xxx:41434 MULTI_sva: pool returned IPv4=10.8.0.2, IPv6=(Not enabled)
May 30 16:54:34 server ovpn-server[62795]: client/178.xxx.xxx.xxx:41434 MULTI: Learn: 10.8.0.2 -> client/178.xxx.xxx.xxx:41434
May 30 16:54:34 server ovpn-server[62795]: client/178.xxx.xxx.xxx:41434 MULTI: primary virtual IP for client/178.xxx.xxx.xxx:41434: 10.8.0.2
...
May 30 16:54:48 server ovpn-server[62795]: client/178.xxx.xxx.xxx:41434 SIGUSR1[soft,connection-reset] received, client-instance restarting

服务器配置文件/etc/openvpn/server.conf #

port 1194
proto tcp
dev tun
user nobody
group nogroup
persist-key
persist-tun
keepalive 10 120
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
push "redirect-gateway def1"
dh none
ecdh-curve prime256v1
tls-crypt tls-crypt.key
crl-verify crl.pem
ca ca.crt
cert server_au1Yf0HuxvBTSYQS.crt
key server_au1Yf0HuxvBTSYQS.key
auth SHA256
cipher AES-128-GCM
ncp-ciphers AES-128-GCM
tls-server
tls-version-min 1.2
tls-cipher TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256
client-config-dir /etc/openvpn/ccd
status /var/log/openvpn/status.log
verb 3

客户端.ovpn配置文件 #

client
proto tcp-client
remote 195.xxx.xxx.xxx
dev tun
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
verify-x509-name server_au1Yf0HuxvBTSYQS name
auth SHA256
auth-nocache
cipher AES-128-GCM
tls-client
tls-version-min 1.2
tls-cipher TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256
#ignore-unknown-option block-outside-dns
setenv opt block-outside-dns # Prevent Windows 10 DNS leak
verb 3

备注：内容来源于stack exchange，提问作者Oleg Golovanov