VPN (PPTP) disconnects in OS X El Capitan (after update) OS X - 10.11.4 El Capitan
Macbook pro Retina Mid 2015
VPN type is PPTP, automatic encryption, All traffic over VPN. 


When connecting to a VPN server, the system mentions that the connection could not be established. The connection was working before the update. 
Here is the log from the console: 

29-03-16 13:21:17,116 nesessionmanager[1014]: NESMLegacySession[VPN (PPTP):F5CF80F6-DB7E-4039-BC09-AD38FE019991]: Received a start command from SystemUIServer[1477]
29-03-16 13:21:17,116 nesessionmanager[1014]: NESMLegacySession[VPN (PPTP):F5CF80F6-DB7E-4039-BC09-AD38FE019991]: status changed to connecting
29-03-16 13:21:17,123 pppd[2023]: NetworkExtension is the controller
29-03-16 13:21:17,123 pppd[2023]: NetworkExtension is the controller
29-03-16 13:21:17,140 pppd[2023]: publish_entry SCDSet() failed: Success!
29-03-16 13:21:17,140 pppd[2023]: publish_entry SCDSet() failed: Success!
29-03-16 13:21:17,140 pppd[2023]: pppd 2.4.2 (Apple version 809.40.5) started by lukevanenkhuizen, uid 501
29-03-16 13:21:17,140 pppd[2023]: pptp_get_router_address
29-03-16 13:21:17,140 pppd[2023]: pptp_get_router_address 192.168.10.254 from dict 1
29-03-16 13:21:17,141 pppd[2023]: PPTP connecting to server '95.97.141.150' (95.97.141.150)...
29-03-16 13:21:30,495 CalendarAgent[304]: [com.apple.calendar.store.log.caldav.coredav] [Refusing to parse response to PROPPATCH because of content-type: [text/plain; charset="utf-8"].]
29-03-16 13:21:30,580 CalendarAgent[304]: [com.apple.calendar.store.log.caldav.coredav] [Refusing to parse response to PROPPATCH because of content-type: [text/plain; charset="utf-8"].]
29-03-16 13:21:32,249 pppd[2023]: PPTP connect errno = 60 Operation timed out
29-03-16 13:21:32,250 nesessionmanager[1014]: NESMLegacySession[VPN (PPTP):F5CF80F6-DB7E-4039-BC09-AD38FE019991]: status changed to disconnecting
29-03-16 13:21:32,252 nesessionmanager[1014]: NESMLegacySession[VPN (PPTP):F5CF80F6-DB7E-4039-BC09-AD38FE019991]: status changed to disconnected, last stop reason None
29-03-16 13:21:32,319 UserNotificationCenter[2026]: *** WARNING: Method userSpaceScaleFactor in class NSWindow is deprecated on 10.7 and later. It should not be used in new applications. Use convertRectToBacking: instead. 
29-03-16 13:21:35,000 syslogd[48]: ASL Sender Statistics


What does this mean? Any help would be highly appreciated!
I've been struggling with VPN since 10.11.4. I'm unable to connect to a VPN server that I've used for a long time. I hope this is not noise, but here's what I have encountered in my research...

My problem is with an L2TP tunnel. https://discussions.apple.com/thread/7502488 discusses a potentially related problem with respect to Cisco IPSec VPN. The interesting part there is that some have reported success changing to Diffie-Hellman group 14.

Slightly related is the App Store description of the 10.11.4 OS X server where they say "L2TP/IPsec VPN profiles now require 2048-bit or stronger Diffie-Hellman groups". This is consistent with the group 14 reports above since group 14 has 2048 bits.

At https://supportforums.cisco.com/document/12276506/diffie-hellman-groups they discuss the relative strengths of the various groups. One post says that group 14 is the minimum acceptable security for key exchange.

So I've started to think that Apple is now ruling out groups 1, 2, and 5. This is bad for me since those are the only groups supported by the older tunnel server I used to connect to.

I also use Private Internet Access sometimes. I tested connecting to them using L2TP. It worked fine. However, even with verbose logging, I couldn't find any log entries related to a negotiated DH group. But PIA is a security focused service. So, I'm guessing they would avoid a DH group considered insecure by some.

I contacted Apple Care. They were unable to help. I didn't push them to escalate it.

I tested from my Mac using wireless, Ethernet, and tethered to my 3G phone. My work partner, running an older mac that hasn't been updated to 10.11.4, connects fine to the server.

I also tested with my iPhone. It cannot connect either. Unfortunately, I've updated that recently to iOS 9.3. forums_developer_apple_com/thread/31608 reports problems with iOS 9.3 in addition to OS X 10.11.4. (Sorry, I don't have enough reputation to post that third link.)

Regards, 
Barry