I want to connect to an l2tp vpn.
everything works fine on Android and Windows but when I try to connect using ubuntu 20.04 it will connect for almost 1 minute then it will get disconnected.
during the time that VPN is connected, I can't open websites
output of journalctl -u NetworkManager.service:
I have replaced the actual IP with AAA.BBB.CCC.DDD
NetworkManager[1146]: <info> [1642422230.4639] manager: NetworkManager state is now CONNECTED_SITE
NetworkManager[1146]: <info> [1642422230.4640] policy: set 'motanroo 2 ' (ppp0) as default for IPv4 routing and DNS
charon[156708]: 10[IKE] sending keep alive to AAA.BBB.CCC.DDD[4500]
NetworkManager[156757]: xl2tpd[156757]: result_code_avp: avp is incorrect size. 8 < 10
NetworkManager[156757]: xl2tpd[156757]: handle_avps: Bad exit status handling attribute 1 (Result Code) on mandatory packet.
NetworkManager[156757]: xl2tpd[156757]: call_close: Call 17885 to AAA.BBB.CCC.DDD disconnected
NetworkManager[156757]: xl2tpd[156757]: check_control: Received out of order control packet on tunnel 806 (got 2, expected 3)
NetworkManager[156757]: xl2tpd[156757]: handle_packet: bad control packet!
NetworkManager[156757]: xl2tpd[156757]: check_control: Received out of order control packet on tunnel 806 (got 2, expected 3)
NetworkManager[156757]: xl2tpd[156757]: handle_packet: bad control packet!
NetworkManager[156757]: xl2tpd[156757]: check_control: Received out of order control packet on tunnel 806 (got 2, expected 3)
NetworkManager[156757]: xl2tpd[156757]: handle_packet: bad control packet!
NetworkManager[156757]: xl2tpd[156757]: check_control: Received out of order control packet on tunnel 806 (got 2, expected 3)
NetworkManager[156757]: xl2tpd[156757]: handle_packet: bad control packet!
charon[156708]: 13[IKE] sending keep alive to AAA.BBB.CCC.DDD[4500]
NetworkManager[156757]: xl2tpd[156757]: check_control: Received out of order control packet on tunnel 806 (got 2, expected 3)
NetworkManager[156757]: xl2tpd[156757]: handle_packet: bad control packet!
charon[156708]: 09[IKE] sending keep alive to AAA.BBB.CCC.DDD[4500]
NetworkManager[156757]: xl2tpd[156757]: Maximum retries exceeded for tunnel 20125. Closing.
NetworkManager[156757]: xl2tpd[156757]: Terminating pppd: sending TERM signal to pid 156758
NetworkManager[156757]: xl2tpd[156757]: Connection 806 closed to AAA.BBB.CCC.DDD, port 1701 (Timeout)
pppd[156758]: Terminating on signal 15
pppd[156758]: Connect time 1.1 minutes.
pppd[156758]: Sent 1297554577 bytes, received 0 bytes.
charon[156708]: 15[KNL] interface ppp0 deactivated
NetworkManager[1146]: <info> [1642422296.2657] device (ppp0): state change: disconnected -> unmanaged (reason 'connection-assumed', sys-iface-state: 'external')
charon[156708]: 05[KNL] 192.168.22.47 disappeared from ppp0
pppd[156758]: Overriding mtu 1500 to 1400
pppd[156758]: Overriding mru 1500 to mtu value 1400
pppd[156758]: Connection terminated.
charon[156708]: 07[KNL] interface ppp0 deleted
NetworkManager[156757]: xl2tpd[156757]: death_handler: Fatal signal 15 received
NetworkManager[1146]: <info> [1642422302.2736] vpn-connection[0x56514d062730,d14b1868-4a7b-4064-8a0b-fee18d6c858c,"motanroo 2 ",62:(ppp0)]: VPN plugin: state changed: stopping (5)
NetworkManager[157440]: Stopping strongSwan IPsec...
charon[156708]: 00[DMN] signal of type SIGINT received. Shutting down
charon[156708]: 00[IKE] closing CHILD_SA d14b1868-4a7b-4064-8a0b-fee18d6c858c{1} with SPIs c0f02b42_i (952 bytes) 08cc91e2_o (1177174634 bytes) and TS 192.168.125.129/32 === AAA.BBB.CCC.DDD/32[udp/l2f]
charon[156708]: 00[IKE] closing CHILD_SA d14b1868-4a7b-4064-8a0b-fee18d6c858c{1} with SPIs c0f02b42_i (952 bytes) 08cc91e2_o (1177174634 bytes) and TS 192.168.125.129/32 === AAA.BBB.CCC.DDD/32[udp/l2f]
charon[156708]: 00[IKE] sending DELETE for ESP CHILD_SA with SPI c0f02b42
charon[156708]: 00[ENC] generating INFORMATIONAL_V1 request 2553143325 [ HASH D ]
charon[156708]: 00[NET] sending packet: from 192.168.125.129[4500] to AAA.BBB.CCC.DDD[4500] (76 bytes)
charon[156708]: 00[IKE] deleting IKE_SA d14b1868-4a7b-4064-8a0b-fee18d6c858c[1] between 192.168.125.129[192.168.125.129]...AAA.BBB.CCC.DDD[AAA.BBB.CCC.DDD]
charon[156708]: 00[IKE] deleting IKE_SA d14b1868-4a7b-4064-8a0b-fee18d6c858c[1] between 192.168.125.129[192.168.125.129]...AAA.BBB.CCC.DDD[AAA.BBB.CCC.DDD]
charon[156708]: 00[IKE] sending DELETE for IKE_SA d14b1868-4a7b-4064-8a0b-fee18d6c858c[1]
charon[156708]: 00[ENC] generating INFORMATIONAL_V1 request 2194498276 [ HASH D ]
charon[156708]: 00[NET] sending packet: from 192.168.125.129[4500] to AAA.BBB.CCC.DDD[4500] (92 bytes)
ipsec_starter[156707]: child 156708 (charon) has quit (exit code 0)
ipsec_starter[156707]:
ipsec_starter[156707]: charon stopped after 200 ms
ipsec_starter[156707]: ipsec starter stopped
pppd[156758]: Modem hangup
pppd[156758]: Exit.
nm-l2tp-service[156670]: ipsec shut down
NetworkManager[1146]: <info> [1642422302.3833] vpn-connection[0x56514d062730,d14b1868-4a7b-4064-8a0b-fee18d6c858c,"motanroo 2 ",62:(ppp0)]: VPN plugin: state changed: stopped (6)
NetworkManager[1146]: <info> [1642422302.3855] manager: NetworkManager state is now CONNECTED_LOCAL
NetworkManager[1146]: <info> [1642422302.3871] manager: NetworkManager state is now CONNECTED_SITE
NetworkManager[1146]: <info> [1642422302.3873] policy: set 'Wired connection 1' (usb0) as default for IPv4 routing and DNS
NetworkManager[1146]: <info> [1642422302.3971] vpn-connection[0x56514d062730,d14b1868-4a7b-4064-8a0b-fee18d6c858c,"motanroo 2 ",0]: VPN service disappeared
