Till today, this website showed me some answers that solve the problem. But it seems I couldn't find the correct answer to this problem.
I have a project for a VPN network for remote service purposes, the network will not be used constantly. I developed C# software for windows clients to set Built-In Windows clients to connect to the company's on-premise server.
The server runs Ubuntu 20.04LTS and I set up Strongswan VPN has 2 clients on it.
Client A and Client B can connect L2TP server without any hassle. Any I can ping to Server from both Clients. When I try to connect with both A and B clients, the server just allows a single device to connect and I can ping the server just a single Client.
What I need pinging from Client A to Client B. I felt can't set ufw firewall or iptables, but not sure where to follow.
Configuration below:
/etc/ipsec.secrets
192.168.0.17 %any : PSK "xpasswordx"
/etc/ppp/chap-secrets
userclientA * xpassx 192.168.30.10
userclientB * xpassx 192.168.30.11
/etc/ipsec.conf
config setup
conn L2TP-PSK-noNAT
dpdaction=clear
authby=secret
auto=add
keyingtries=3
ikelifetime=8h
keylife=1h
keyexchange = ikev1
ike=aes256-aes192-aes128-sha384-sha256-sha1-modp2048-modp1536-modp1024!
type=transport
left=192.168.0.17
leftprotoport=17/1701
right=%any
rightprotoport=17/%any
/etc/xl2tpd/xl2tpd.conf
[global]
ipsec saref = yes
saref refinfo = 30
;debug avp = yes
;debug network = yes
;debug state = yes
;debug tunnel = yes
[lns default]
ip range = 192.168.30.2-192.168.30.254
local ip = 192.168.30.1
refuse pap = yes
require authentication = yes
;ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes
/etc/ppp/options.xl2tpd
logfd 2
logfile /var/log/xl2tpns.log
refuse-mschap-v2
refuse-mschap
ms-dns 8.8.8.8
ms-dns 8.8.4.4
asyncmap 0
auth
crtscts
idle 1800
mtu 1200
mru 1200
lock
hide-password
local
#debug
name l2tpd
proxyarp
lcp-echo-interval 30
lcp-echo-failure 4
iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT udp -- anywhere anywhere policy match dir in pol ipsec udp dpt:l2f
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
/etc/sysctl.conf
net.ipv4.ip_forward = 1
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.rp_filter = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.icmp_ignore_bogus_error_responses = 1
