I've installed l2tp-ipsec-vpn but when I try to connect to the vpn server I get error 500. Here are the logs: Jun 17 12:54:37.449 ipsec_setup: Stopping Openswan IPsec... Jun 17 12:54:38.858 Stopping xl2tpd: xl2tpd. Jun 17 12:54:38.859 xl2tpd[1511]: death_handler: Fatal signal 15 received Jun 17 12:54:38.872 ipsec_setup: Starting Openswan IPsec U2.6.37/K3.2.0-23-generic... Jun 17 12:54:39.027 ipsec__plutorun: Starting Pluto subsystem... Jun 17 12:54:39.033 ipsec__plutorun: adjusting ipsec.d to /etc/ipsec.d Jun 17 12:54:39.037 recvref[30]: Protocol not available Jun 17 12:54:39.038 xl2tpd[2442]: This binary does not support kernel L2TP. Jun 17 12:54:39.038 xl2tpd[2444]: xl2tpd version xl2tpd-1.3.1 started on atp-ThinkPad-SL410 PID:2444 Jun 17 12:54:39.038 xl2tpd[2444]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc. Jun 17 12:54:39.038 xl2tpd[2444]: Forked by Scott Balmos and David Stipp, (C) 2001 Jun 17 12:54:39.038 xl2tpd[2444]: Inherited by Jeff McAdams, (C) 2002 Jun 17 12:54:39.039 xl2tpd[2444]: Forked again by Xelerance (www.xelerance.com) (C) 2006 Jun 17 12:54:39.039 xl2tpd[2444]: Listening on IP address 0.0.0.0, port 1701 Jun 17 12:54:39.040 Starting xl2tpd: xl2tpd. Jun 17 12:54:39.062 ipsec__plutorun: 002 added connection description "L2TP" Jun 17 12:55:30.753 104 "L2TP" #1: STATE_MAIN_I1: initiate Jun 17 12:55:30.754 010 "L2TP" #1: STATE_MAIN_I1: retransmission; will wait 20s for response Jun 17 12:55:30.754 010 "L2TP" #1: STATE_MAIN_I1: retransmission; will wait 40s for response Jun 17 12:55:30.754 003 "L2TP" #1: ignoring Vendor ID payload [MS NT5 ISAKMPOAKLEY 00000008] Jun 17 12:55:30.754 003 "L2TP" #1: received Vendor ID payload [RFC 3947] method set to=109 Jun 17 12:55:30.754 003 "L2TP" #1: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-02_n] meth=106, but already using method 109 Jun 17 12:55:30.755 003 "L2TP" #1: ignoring Vendor ID payload [FRAGMENTATION] Jun 17 12:55:30.755 003 "L2TP" #1: ignoring Vendor ID payload [MS-Negotiation Discovery Capable] Jun 17 12:55:30.755 003 "L2TP" #1: ignoring Vendor ID payload [IKE CGA version 1] Jun 17 12:55:30.755 106 "L2TP" #1: STATE_MAIN_I2: sent MI2, expecting MR2 Jun 17 12:55:30.755 010 "L2TP" #1: STATE_MAIN_I2: retransmission; will wait 20s for response Jun 17 12:55:30.755 003 "L2TP" #1: NAT-Traversal: Result using RFC 3947 (NAT-Traversal): i am NATed Jun 17 12:55:30.755 108 "L2TP" #1: STATE_MAIN_I3: sent MI3, expecting MR3 Jun 17 12:55:30.756 004 "L2TP" #1: STATE_MAIN_I4: ISAKMP SA established {auth=OAKLEY_PRESHARED_KEY cipher=oakley_3des_cbc_192 prf=oakley_sha group=modp1024} Jun 17 12:55:30.756 117 "L2TP" #2: STATE_QUICK_I1: initiate Jun 17 12:55:30.756 010 "L2TP" #2: STATE_QUICK_I1: retransmission; will wait 20s for response Jun 17 12:55:30.756 003 "L2TP" #2: ignoring informational payload, type IPSEC_RESPONDER_LIFETIME msgid=6b03ff69 Jun 17 12:55:30.756 003 "L2TP" #2: NAT-Traversal: received 2 NAT-OA. ignored because peer is not NATed Jun 17 12:55:30.756 003 "L2TP" #2: our client subnet returned doesn't match my proposal - us:192.168.1.3/32 vs them:109.162.174.235/32 Jun 17 12:55:30.757 003 "L2TP" #2: Allowing questionable proposal anyway [ALLOW_MICROSOFT_BAD_PROPOSAL] Jun 17 12:55:30.757 004 "L2TP" #2: STATE_QUICK_I2: sent QI2, IPsec SA established transport mode {ESP=>0x23af21f8 <0xdb4a87b6 xfrm=AES_128-HMAC_SHA1 NATOA=none NATD=none DPD=none} Jun 17 12:55:31.759 xl2tpd[2444]: Connecting to host x.x.x.x, port 1701 Jun 17 12:55:32.021 xl2tpd[2444]: Connection established to x.x.x.x, 1701. Local: 4720, Remote: 200 (ref=0/0). Jun 17 12:55:32.023 xl2tpd[2444]: Calling on tunnel 4720 Jun 17 12:55:32.454 xl2tpd[2444]: Call established with x.x.x.x, Local: 9667, Remote: 3, Serial: 1 (ref=0/0) Jun 17 12:55:32.456 xl2tpd[2444]: start_pppd: I'm running: Jun 17 12:55:32.456 xl2tpd[2444]: "/usr/sbin/pppd" Jun 17 12:55:32.457 xl2tpd[2444]: "passive" Jun 17 12:55:32.458 xl2tpd[2444]: "nodetach" Jun 17 12:55:32.458 xl2tpd[2444]: ":" Jun 17 12:55:32.459 xl2tpd[2444]: "file" Jun 17 12:55:32.459 xl2tpd[2444]: "/etc/ppp/L2TP.options.xl2tpd" Jun 17 12:55:32.460 xl2tpd[2444]: "ipparam" Jun 17 12:55:32.461 xl2tpd[2444]: "x.x.x.x" Jun 17 12:55:32.462 xl2tpd[2444]: "/dev/pts/1" Jun 17 12:55:32.583 pppd[2711]: Plugin passprompt.so loaded. Jun 17 12:55:32.583 pppd[2711]: pppd 2.4.5 started by root, uid 0 Jun 17 12:55:32.619 pppd[2711]: Using interface ppp0 Jun 17 12:55:32.620 pppd[2711]: Connect: ppp0 <--> /dev/pts/1 Jun 17 12:55:33.693 pppd[2711]: /usr/bin/L2tpIPsecVpn exited with code 0 Jun 17 12:55:34.454 [ERROR 404] Authentication failed: closing connection to 'L2TP' Jun 17 12:55:34.456 pppd[2711]: MS-CHAP authentication failed: E=691 Authentication failure Jun 17 12:55:34.457 pppd[2711]: CHAP authentication failed Jun 17 12:55:34.461 Stopping xl2tpd: xl2tpd. Jun 17 12:55:34.462 xl2tpd[2444]: death_handler: Fatal signal 15 received Jun 17 12:55:34.463 pppd[2711]: Modem hangup Jun 17 12:55:34.463 pppd[2711]: Connection terminated. Jun 17 12:55:34.474 ipsec_setup: Stopping Openswan IPsec... Jun 17 12:55:34.482 pppd[2711]: Exit. Jun 17 12:55:35.587 ipsec_setup: ERROR: Module xfrm4_mode_transport is in use Jun 17 12:55:35.665 ipsec_setup: ERROR: Module esp4 is in use I had this problem by ubuntu 11.10 though I can easily connect to the server from windows. I use ubuntu 12.0 64bit