server cant get more than350mbps at most

[jamesbh]

I have setup Openvpn on centos Server
it is a dedicated server
the problem is that it cant handle more than 300~350mbps of traffic for 6,000 concurrent users on a 1gbps Network Card
I guessed it might be because of centos7 issue
I setup another server with centos8 and for new users I forwarded them to the new server
but still both servers cant get more than 300mbps
I thought it might be the onboard network card issue with less PPS able to handle so I replaced with a 10Gbps network card but unfortunatly it became worst
what can I do to fix this issue

View OriginalClient config

client
dev tun
proto udp
remote IP 443
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
auth SHA512
cipher AES-256-CBC
ignore-unknown-option block-outside-dns
block-outside-dns
verb 3
<ca>

View OriginalServer config

port 443
proto udp
dev tun
ca ca.crt
cert server.crt
key server.key
dh dh.pem
auth SHA512
tls-crypt tc.key
topology subnet
server 10.8.0.0 255.255.0.0
max-clients 65000
push "redirect-gateway def1 bypass-dhcp"
ifconfig-pool-persist ipp.txt
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
keepalive 10 120
cipher AES-256-CBC
user nobody
group nobody
persist-key
persist-tun
duplicate-cn
;status openvpn-status.log
verb 5
crl-verify crl.pem
explicit-exit-notify
status /etc/openvpn/server/openvpn-status.log
log /etc/openvpn/server/openvpn.log

thx

[300000]

You can run multi instance of openvpn so it can handle that user base . 350 is fast not slow and openvpn is single thread so your cpu not use at full. If you can config multi instance it can use full cpu power.