Ubuntu – Failure to connect to a L2TP VPN over IPSec on Ubuntu 16.04

ipsecl2tpUbuntuvpn

I am having issues connecting to my company's L2TP VPN over IPSEC. This is a Pelink Balance 305 router which has been configured correctly. I have checked that other colleagues have been able to connect using the same settings.

I am running ubuntu 16.04. I have tried the same setup in a ubuntu 18.04/20.04 VM with the same results.

I've double checked the username/password/pre-shared-key, and all looks well there.

The error I see when I try to connect is as follows.

The VPN connection 'VPN Name' disconnected because the VPN service stopped.

Below is the /var/log/syslog during the connection attempt. Does anyone have any thoughts or suggestions? Thanks

May  5 14:35:10 iboy gnome-session[3866]: "No such interface 'org.freedesktop.DBus.Properties' on object at path /org/freedesktop/NetworkManager/ActiveConnection/21"
May  5 14:41:57 iboy NetworkManager[1606]: <info>  [1588704117.5731] audit: op="connection-activate" uuid="a8ea33a2-b60c-4c93-80b5-8165e59150dd" name="<VPN-NAME> VPN" pid=4114 uid=1001 result="success"
May  5 14:41:57 iboy NetworkManager[1606]: <info>  [1588704117.5773] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: Started the VPN service, PID 24848
May  5 14:41:57 iboy NetworkManager[1606]: <info>  [1588704117.5842] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: Saw the service appear; activating connection
May  5 14:41:57 iboy NetworkManager[1606]: <info>  [1588704117.6464] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN connection: (ConnectInteractive) reply received
May  5 14:41:57 iboy NetworkManager[1606]: nm-l2tp[24848] <info>  ipsec enable flag: yes
May  5 14:41:57 iboy NetworkManager[1606]: ** Message: Check port 1701
May  5 14:41:57 iboy NetworkManager[1606]: nm-l2tp[24848] <info>  starting ipsec
May  5 14:41:57 iboy NetworkManager[1606]: Stopping strongSwan IPsec failed: starter is not running
May  5 14:41:59 iboy NetworkManager[1606]: Starting strongSwan 5.3.5 IPsec [starter]...
May  5 14:41:59 iboy NetworkManager[1606]: Loading config setup
May  5 14:41:59 iboy NetworkManager[1606]: Loading conn 'a8ea33a2-b60c-4c93-80b5-8165e59150dd'
May  5 14:41:59 iboy NetworkManager[1606]: found netkey IPsec stack
May  5 14:41:59 iboy charon: 00[DMN] Starting IKE charon daemon (strongSwan 5.3.5, Linux 4.15.0-50-generic, x86_64)
May  5 14:41:59 iboy charon: 00[CFG] disabling load-tester plugin, not configured
May  5 14:41:59 iboy charon: 00[LIB] plugin 'load-tester': failed to load - load_tester_plugin_create returned NULL
May  5 14:41:59 iboy charon: 00[CFG] dnscert plugin is disabled
May  5 14:41:59 iboy charon: 00[CFG] ipseckey plugin is disabled
May  5 14:41:59 iboy charon: 00[CFG] attr-sql plugin: database URI not set
May  5 14:41:59 iboy charon: 00[CFG] loading ca certificates from '/etc/ipsec.d/cacerts'
May  5 14:41:59 iboy charon: 00[CFG] loading aa certificates from '/etc/ipsec.d/aacerts'
May  5 14:41:59 iboy charon: 00[CFG] loading ocsp signer certificates from '/etc/ipsec.d/ocspcerts'
May  5 14:41:59 iboy charon: 00[CFG] loading attribute certificates from '/etc/ipsec.d/acerts'
May  5 14:41:59 iboy charon: 00[CFG] loading crls from '/etc/ipsec.d/crls'
May  5 14:41:59 iboy charon: 00[CFG] loading secrets from '/etc/ipsec.secrets'
May  5 14:41:59 iboy charon: 00[CFG] loading secrets from '/etc/ipsec.d/ipsec.nm-l2tp.secrets'
May  5 14:41:59 iboy charon: 00[CFG]   loaded IKE secret for %any
May  5 14:41:59 iboy charon: 00[CFG] sql plugin: database URI not set
May  5 14:41:59 iboy charon: 00[CFG] opening triplet file /etc/ipsec.d/triplets.dat failed: No such file or directory
May  5 14:41:59 iboy charon: 00[CFG] eap-simaka-sql database URI missing
May  5 14:41:59 iboy charon: 00[CFG] loaded 0 RADIUS server configurations
May  5 14:41:59 iboy charon: 00[CFG] no threshold configured for systime-fix, disabled
May  5 14:41:59 iboy charon: 00[CFG] coupling file path unspecified
May  5 14:41:59 iboy charon: 00[LIB] loaded plugins: charon test-vectors unbound ldap pkcs11 aes rc2 sha1 sha2 md4 md5 rdrand random nonce x509 revocation constraints acert pubkey pkcs1 pkcs7 pkcs8 pkcs12 pgp dnskey sshkey dnscert ipseckey pem openssl gcrypt af-alg fips-prf gmp agent chapoly xcbc cmac hmac ctr ccm gcm ntru bliss curl soup mysql sqlite attr kernel-netlink resolve socket-default connmark farp stroke updown eap-identity eap-sim eap-sim-pcsc eap-aka eap-aka-3gpp2 eap-simaka-pseudonym eap-simaka-reauth eap-md5 eap-gtc eap-mschapv2 eap-dynamic eap-radius eap-tls eap-ttls eap-peap eap-tnc xauth-generic xauth-eap xauth-pam xauth-noauth tnc-tnccs tnccs-20 tnccs-11 tnccs-dynamic dhcp whitelist lookip error-notify certexpire led radattr addrblock unity
May  5 14:41:59 iboy charon: 00[LIB] dropped capabilities, running as uid 0, gid 0
May  5 14:41:59 iboy charon: 00[JOB] spawning 16 worker threads
May  5 14:41:59 iboy charon: 03[CFG] received stroke: add connection 'a8ea33a2-b60c-4c93-80b5-8165e59150dd'
May  5 14:41:59 iboy charon: 03[CFG] added configuration 'a8ea33a2-b60c-4c93-80b5-8165e59150dd'
May  5 14:42:00 iboy charon: 05[CFG] rereading secrets
May  5 14:42:00 iboy charon: 05[CFG] loading secrets from '/etc/ipsec.secrets'
May  5 14:42:00 iboy charon: 05[CFG] loading secrets from '/etc/ipsec.d/ipsec.nm-l2tp.secrets'
May  5 14:42:00 iboy charon: 05[CFG]   loaded IKE secret for %any
May  5 14:42:00 iboy NetworkManager[1606]: nm-l2tp[24848] <info>  Spawned ipsec up script with PID 24930.
May  5 14:42:00 iboy charon: 07[CFG] received stroke: initiate 'a8ea33a2-b60c-4c93-80b5-8165e59150dd'
May  5 14:42:00 iboy charon: 08[IKE] initiating Main Mode IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1] to <REDACTED-IP>
May  5 14:42:00 iboy charon: 08[ENC] generating ID_PROT request 0 [ SA V V V V ]
May  5 14:42:00 iboy charon: 08[NET] sending packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (212 bytes)
May  5 14:42:00 iboy charon: 10[NET] received packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (132 bytes)
May  5 14:42:00 iboy charon: 10[ENC] parsed ID_PROT response 0 [ SA V V V ]
May  5 14:42:00 iboy charon: 10[IKE] received XAuth vendor ID
May  5 14:42:00 iboy charon: 10[IKE] received DPD vendor ID
May  5 14:42:00 iboy charon: 10[IKE] received NAT-T (RFC 3947) vendor ID
May  5 14:42:00 iboy charon: 10[ENC] generating ID_PROT request 0 [ KE No NAT-D NAT-D ]
May  5 14:42:00 iboy charon: 10[NET] sending packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (244 bytes)
May  5 14:42:00 iboy charon: 11[NET] received packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (244 bytes)
May  5 14:42:00 iboy charon: 11[ENC] parsed ID_PROT response 0 [ KE No NAT-D NAT-D ]
May  5 14:42:00 iboy charon: 11[IKE] local host is behind NAT, sending keep alives
May  5 14:42:00 iboy charon: 11[ENC] generating ID_PROT request 0 [ ID HASH ]
May  5 14:42:00 iboy charon: 11[NET] sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (68 bytes)
May  5 14:42:00 iboy charon: 12[NET] received packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (68 bytes)
May  5 14:42:00 iboy charon: 12[ENC] parsed ID_PROT response 0 [ ID HASH ]
May  5 14:42:00 iboy charon: 12[IKE] IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1] established between <REDACTED-IP>[<REDACTED-IP>]...<REDACTED-IP>[<REDACTED-IP>]
May  5 14:42:00 iboy charon: 12[IKE] scheduling reauthentication in 10209s
May  5 14:42:00 iboy charon: 12[IKE] maximum IKE_SA lifetime 10749s
May  5 14:42:00 iboy charon: 12[ENC] generating QUICK_MODE request 3641543042 [ HASH SA No ID ID NAT-OA NAT-OA ]
May  5 14:42:00 iboy charon: 12[NET] sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (220 bytes)
May  5 14:42:00 iboy charon: 13[NET] received packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (196 bytes)
May  5 14:42:00 iboy charon: 13[ENC] parsed QUICK_MODE response 3641543042 [ HASH SA No ID ID NAT-OA NAT-OA ]
May  5 14:42:00 iboy charon: 13[IKE] CHILD_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd{1} established with SPIs cfaeea5a_i cb4148e7_o and TS <REDACTED-IP>/32[udp/l2f] === <REDACTED-IP>/32[udp/l2f]
May  5 14:42:00 iboy NetworkManager[1606]: initiating Main Mode IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1] to <REDACTED-IP>
May  5 14:42:00 iboy NetworkManager[1606]: generating ID_PROT request 0 [ SA V V V V ]
May  5 14:42:00 iboy NetworkManager[1606]: sending packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (212 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: received packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (132 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: parsed ID_PROT response 0 [ SA V V V ]
May  5 14:42:00 iboy NetworkManager[1606]: received XAuth vendor ID
May  5 14:42:00 iboy NetworkManager[1606]: received DPD vendor ID
May  5 14:42:00 iboy NetworkManager[1606]: received NAT-T (RFC 3947) vendor ID
May  5 14:42:00 iboy NetworkManager[1606]: generating ID_PROT request 0 [ KE No NAT-D NAT-D ]
May  5 14:42:00 iboy NetworkManager[1606]: sending packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (244 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: received packet: from <REDACTED-IP>[500] to <REDACTED-IP>[500] (244 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: parsed ID_PROT response 0 [ KE No NAT-D NAT-D ]
May  5 14:42:00 iboy NetworkManager[1606]: local host is behind NAT, sending keep alives
May  5 14:42:00 iboy NetworkManager[1606]: generating ID_PROT request 0 [ ID HASH ]
May  5 14:42:00 iboy NetworkManager[1606]: sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (68 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: received packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (68 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: parsed ID_PROT response 0 [ ID HASH ]
May  5 14:42:00 iboy NetworkManager[1606]: IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1] established between <REDACTED-IP>[<REDACTED-IP>]...<REDACTED-IP>[<REDACTED-IP>]
May  5 14:42:00 iboy NetworkManager[1606]: scheduling reauthentication in 10209s
May  5 14:42:00 iboy NetworkManager[1606]: maximum IKE_SA lifetime 10749s
May  5 14:42:00 iboy NetworkManager[1606]: generating QUICK_MODE request 3641543042 [ HASH SA No ID ID NAT-OA NAT-OA ]
May  5 14:42:00 iboy NetworkManager[1606]: sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (220 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: received packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (196 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: parsed QUICK_MODE response 3641543042 [ HASH SA No ID ID NAT-OA NAT-OA ]
May  5 14:42:00 iboy NetworkManager[1606]: CHILD_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd{1} established with SPIs cfaeea5a_i cb4148e7_o and TS <REDACTED-IP>/32[udp/l2f] === <REDACTED-IP>/32[udp/l2f]
May  5 14:42:00 iboy NetworkManager[1606]: generating QUICK_MODE request 3641543042 [ HASH ]
May  5 14:42:00 iboy NetworkManager[1606]: connection 'a8ea33a2-b60c-4c93-80b5-8165e59150dd' established successfully
May  5 14:42:00 iboy charon: 13[ENC] generating QUICK_MODE request 3641543042 [ HASH ]
May  5 14:42:00 iboy charon: 13[NET] sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (60 bytes)
May  5 14:42:00 iboy NetworkManager[1606]: nm-l2tp[24848] <info>  strongSwan IPsec tunnel is up.
May  5 14:42:00 iboy NetworkManager[1606]: ** Message: xl2tpd started with pid 24939
May  5 14:42:00 iboy NetworkManager[1606]: xl2tpd[24939]: Not looking for kernel SAref support.
May  5 14:42:00 iboy NetworkManager[1606]: xl2tpd[24939]: Using l2tp kernel support.
May  5 14:42:00 iboy NetworkManager[1606]: xl2tpd[24939]: xl2tpd version xl2tpd-1.3.6 started on iboy PID:24939
May  5 14:42:00 iboy NetworkManager[1606]: xl2tpd[24939]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc.
May  5 14:42:00 iboy NetworkManager[1606]: xl2tpd[24939]: Forked by Scott Balmos and David Stipp, (C) 2001
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Inherited by Jeff McAdams, (C) 2002
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Forked again by Xelerance (www.xelerance.com) (C) 2006
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Listening on IP address 0.0.0.0, port 1701
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Connecting to host <REDACTED-IP>, port 1701
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704120.9973] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN plugin: state changed: starting (3)
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Connection established to <REDACTED-IP>, 1701.  Local: 9631, Remote: 25790 (ref=0/0).
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Calling on tunnel 9631
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Call established with <REDACTED-IP>, Local: 12163, Remote: 31252, Serial: 1 (ref=0/0)
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: start_pppd: I'm running:
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "/usr/sbin/pppd"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "passive"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "nodetach"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: ":"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "file"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "/var/run/nm-l2tp-a8ea33a2-b60c-4c93-80b5-8165e59150dd/ppp-options"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "plugin"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "pppol2tp.so"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "pppol2tp"
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: "7"
May  5 14:42:01 iboy pppd[24940]: Plugin /usr/lib/pppd/2.4.7/nm-l2tp-pppd-plugin.so loaded.
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] initializing
May  5 14:42:01 iboy pppd[24940]: Plugin pppol2tp.so loaded.
May  5 14:42:01 iboy pppd[24940]: pppd 2.4.7 started by root, uid 0
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 3 / phase 'serial connection'
May  5 14:42:01 iboy pppd[24940]: Using interface ppp0
May  5 14:42:01 iboy pppd[24940]: Connect: ppp0 <-->
May  5 14:42:01 iboy NetworkManager[1606]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 5 / phase 'establish'
May  5 14:42:01 iboy pppd[24940]: Overriding mtu 1500 to 1400
May  5 14:42:01 iboy pppd[24940]: Overriding mru 1500 to mtu value 1400
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.0885] manager: (ppp0): new Generic device (/org/freedesktop/NetworkManager/Devices/20)
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.1045] devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.1045] device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 6 / phase 'authenticate'
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] passwd-hook: requesting credentials...
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] passwd-hook: got credentials from NetworkManager-l2tp
May  5 14:42:01 iboy pppd[24940]: MS-CHAP authentication failed: Access denied
May  5 14:42:01 iboy pppd[24940]: CHAP authentication failed
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 10 / phase 'terminate'
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 5 / phase 'establish'
May  5 14:42:01 iboy pppd[24940]: Overriding mtu 1500 to 1400
May  5 14:42:01 iboy pppd[24940]: Overriding mru 1500 to mtu value 1400
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 11 / phase 'disconnect'
May  5 14:42:01 iboy pppd[24940]: Connection terminated.
May  5 14:42:01 iboy NetworkManager[1606]: nm-l2tp[24848] <info>  Terminated xl2tpd daemon with PID 24939.
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: death_handler: Fatal signal 15 received
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Terminating pppd: sending TERM signal to pid 24940
May  5 14:42:01 iboy NetworkManager[1606]: xl2tpd[24939]: Connection 25790 closed to <REDACTED-IP>, port 1701 (Server closing)
May  5 14:42:01 iboy charon: 10[KNL] interface ppp0 deleted
May  5 14:42:01 iboy NetworkManager[1606]: <warn>  [1588704121.1931] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN plugin: failed: connect-failed (1)
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.1932] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN plugin: state changed: stopping (5)
May  5 14:42:01 iboy NetworkManager[1606]: <error> [1588704121.1938] platform-linux: do-change-link[21]: failure changing link: failure 19 (No such device)
May  5 14:42:01 iboy NetworkManager[1606]: <warn>  [1588704121.1938] device (ppp0): failed to disable userspace IPv6LL address handling
May  5 14:42:01 iboy NetworkManager[1606]: Stopping strongSwan IPsec...
May  5 14:42:01 iboy charon: 00[DMN] signal of type SIGINT received. Shutting down
May  5 14:42:01 iboy charon: 00[IKE] closing CHILD_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd{1} with SPIs cfaeea5a_i (537 bytes) cb4148e7_o (608 bytes) and TS <REDACTED-IP>/32[udp/l2f] === <REDACTED-IP>/32[udp/l2f]
May  5 14:42:01 iboy charon: 00[IKE] sending DELETE for ESP CHILD_SA with SPI cfaeea5a
May  5 14:42:01 iboy charon: 00[ENC] generating INFORMATIONAL_V1 request 963606250 [ HASH D ]
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.1966] devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
May  5 14:42:01 iboy charon: 00[NET] sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (76 bytes)
May  5 14:42:01 iboy charon: 00[IKE] deleting IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1] between <REDACTED-IP>[<REDACTED-IP>]...<REDACTED-IP>[<REDACTED-IP>]
May  5 14:42:01 iboy charon: 00[IKE] sending DELETE for IKE_SA a8ea33a2-b60c-4c93-80b5-8165e59150dd[1]
May  5 14:42:01 iboy charon: 00[ENC] generating INFORMATIONAL_V1 request 1099594777 [ HASH D ]
May  5 14:42:01 iboy charon: 00[NET] sending packet: from <REDACTED-IP>[4500] to <REDACTED-IP>[4500] (84 bytes)
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] phasechange: status 1 / phase 'dead'
May  5 14:42:01 iboy pppd[24940]: nm-l2tp[24848] <info>  [helper-24940] exit: cleaning up
May  5 14:42:01 iboy pppd[24940]: Exit.
May  5 14:42:01 iboy NetworkManager[1606]: ** Message: ipsec shut down
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.2990] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN plugin: state changed: stopped (6)
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.2998] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN plugin: state change reason: unknown (0)
May  5 14:42:01 iboy NetworkManager[1606]: <info>  [1588704121.3005] vpn-connection[0x14d83a0,a8ea33a2-b60c-4c93-80b5-8165e59150dd,"<VPN-NAME> VPN",0]: VPN service disappeared
May  5 14:42:01 iboy gnome-session[3866]: "No such interface 'org.freedesktop.DBus.Properties' on object at path /org/freedesktop/NetworkManager/ActiveConnection/22"

Best Answer

May  5 14:42:01 pppd[24940]: MS-CHAP authentication failed: Access denied
May  5 14:42:01 pppd[24940]: CHAP authentication failed

This is for the L2TP PPP settings and user authentication. The PSK is fine as the IPsec connection was successful.

PPPD authentication failures are usually the result of the username and/or password being incorrect. Perhaps you might need to specify the NT Domain like when connecting to a Windows VPN server, or you might need to use username@domain syntax for the username.

Does the Pelink Balance 305 router's logs have anything useful to indicate what is going wrong with the username and/or password or otherwise?