I set up my VPN server with strongSwan and xl2tpd on Ubuntu server 16.04.
After configuring, I tried to connect from a iPad, but got the errors as follows:
Mar 26 02:22:13 myname-ubuntu-server charon: 01[NET] received packet: from 61.205.5.249[44919] to 192.168.193.3[500] (788 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 01[ENC] parsed ID_PROT request 0 [ SA V V V V V V V V V V V V ]
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received NAT-T (RFC 3947) vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-08 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-07 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-06 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-05 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-04 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-03 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-02 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-02\n vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received FRAGMENTATION vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received DPD vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] 61.205.5.249 is initiating a Main Mode IKE_SA
Mar 26 02:22:13 myname-ubuntu-server charon: 01[ENC] generating ID_PROT response 0 [ SA V V V ]
Mar 26 02:22:13 myname-ubuntu-server charon: 01[NET] sending packet: from 192.168.193.3[500] to 61.205.5.249[44919] (136 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 10[NET] received packet: from 61.205.5.249[44919] to 192.168.193.3[500] (380 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 10[ENC] parsed ID_PROT request 0 [ KE No NAT-D NAT-D ]
Mar 26 02:22:13 myname-ubuntu-server charon: 10[IKE] local host is behind NAT, sending keep alives
Mar 26 02:22:13 myname-ubuntu-server charon: 10[IKE] remote host is behind NAT
Mar 26 02:22:13 myname-ubuntu-server charon: 10[ENC] generating ID_PROT response 0 [ KE No NAT-D NAT-D ]
Mar 26 02:22:13 myname-ubuntu-server charon: 10[NET] sending packet: from 192.168.193.3[500] to 61.205.5.249[44919] (396 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 06[NET] received packet: from 61.205.5.249[4500] to 192.168.193.3[4500] (108 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 06[ENC] parsed ID_PROT request 0 [ ID HASH N(INITIAL_CONTACT) ]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[CFG] looking for pre-shared key peer configs matching 192.168.193.3...61.205.5.249[100.75.130.131]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[IKE] found 1 matching config, but none allows pre-shared key authentication using Main Mode
Mar 26 02:22:13 myname-ubuntu-server charon: 06[ENC] generating INFORMATIONAL_V1 request 2960834334 [ HASH N(AUTH_FAILED) ]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[NET] sending packet: from 192.168.193.3[4500] to 61.205.5.249[4500] (108 bytes)
I thought the critical point of the error is "found 1 matching config, but none allows pre-shared key authentication using Main Mode".
Do anyone know how to resolve this error?
I found a answer for this problem that suggested to add "aggressiveness=yes" to /etc/ipsec.conf and tried but didn't work…
(Maybe I add the line "aggressiveness=yes" in a wrong position… I'm a beginner in Linux…)
I set up config files by following this site:
http://qiita.com/namoshika/items/30c348b56474d422ef64
(I'm sorry but it's written in Japanese…I think you can read code parts at least.)
If someone tell me reliable instruction documents for setting up VPN server on Ubuntu16.04 with L2TP/IPsec, I would appreciate it.
Best Answer
Don't use the aggressive mode, the connection will be less secure. Anyway try with this configuration. I use it on a my VPN Server with strongswan-5.3.5 and xl2tpd-1.3.6
ipsec.conf
ipsec.secrets
/etc/xl2tpd/xl2tpd.conf
/etc/ppp/options.xl2tpd
/etc/ppp/chap-secrets
restart services