The L2TP-VPN server did not respond

Hi,

I updated my macmini server (mid 2011, 2 Ghz Intel Core i7, 8GB RAM, 1TB Disk) last weekend to 10.11.3. The VPN server started malfunctioning around the same time. ThnX in advance for any pointers what I could try to get the VPN server back up and running again.

Note: I have verified the router and the external IP and portmapping has not changed. No other software has been installed except the OSX update and a printer update from EPSON.

1) VPN clients trying to connect get this error message => The L2TP-VPN server did not respond

2) At the same time I can see the following message in the system.log:

Feb 5 23:34:10 mymacmini symptomsd[224]: nw_interface_create_with_name netutil_ifname_to_ifindex(iptap0) failed, dumping backtrace:

[x86_64] libnetcore-583.20.10

0 libsystem_network.dylib 0x00007fff928a6ba5 __nw_create_backtrace_string + 123

1 libsystem_network.dylib 0x00007fff928c7acb nw_interface_create_with_name + 179

2 Network 0x00007fff9185002c -[NWInterface initWithInterfaceName:] + 120

3 SymptomEvaluator 0x00007fff86915918 config_callback + 874

4 SystemConfiguration 0x00007fff98cc2fbf rlsPerform + 184

5 SystemConfiguration 0x00007fff98cd63bb __SCDynamicStoreSetDispatchQueue_block_invoke_2 + 52

6 libdispatch.dylib 0x00007fff877ae871 _dispatch_call_block_and_release + 12

7 libdispatch.dylib 0x00007fff877a333f _dispatch_client_callout + 8

8 libdispatch.dylib 0x00007fff877a7f6f _dispatch_queue_drain + 754

9 libdispatch.dylib 0x00007fff877ae63b _dispatch_queue_invoke + 549

10 libdispatch.dylib 0x00007fff877a6c87 _dispatch_root_queue_drain + 538

11 libdispatch.dylib 0x00007fff877a6a34 _dispatch_worker_thread3 + 91

12 libsystem_pthread.dylib 0x00007fff8e4b268f _pthread_wqthread + 1129

13 libsystem_pthread.dylib 0x00007fff8e4b0365 start_wqthread + 13

Feb 5 23:34:10 mymacmini symptomsd[224]: -[NWInterface initWithInterfaceName:] nw_interface_create_with_name(iptap0) failed, dumping backtrace:

[x86_64] libnetcore-583.20.10

0 libsystem_network.dylib 0x00007fff928a6ba5 __nw_create_backtrace_string + 123

1 Network 0x00007fff91850096 -[NWInterface initWithInterfaceName:] + 226

2 SymptomEvaluator 0x00007fff86915918 config_callback + 874

3 SystemConfiguration 0x00007fff98cc2fbf rlsPerform + 184

4 SystemConfiguration 0x00007fff98cd63bb __SCDynamicStoreSetDispatchQueue_block_invoke_2 + 52

5 libdispatch.dylib 0x00007fff877ae871 _dispatch_call_block_and_release + 12

6 libdispatch.dylib 0x00007fff877a333f _dispatch_client_callout + 8

7 libdispatch.dylib 0x00007fff877a7f6f _dispatch_queue_drain + 754

8 libdispatch.dylib 0x00007fff877ae63b _dispatch_queue_invoke + 549

9 libdispatch.dylib 0x00007fff877a6c87 _dispatch_root_queue_drain + 538

10 libdispatch.dylib 0x00007fff877a6a34 _dispatch_worker_thread3 + 91

11 libsystem_pthread.dylib 0x00007fff8e4b268f _pthread_wqthread + 1129

12 libsystem_pthread.dylib 0x00007fff8e4b0365 start_wqthread + 13

Feb 5 23:34:10 mymacmini symptomsd[224]: nw_interface_create_with_name netutil_ifname_to_ifindex(iptap0) failed, dumping backtrace:

[x86_64] libnetcore-583.20.10

0 libsystem_network.dylib 0x00007fff928a6ba5 __nw_create_backtrace_string + 123

1 libsystem_network.dylib 0x00007fff928c7acb nw_interface_create_with_name + 179

2 Network 0x00007fff9185002c -[NWInterface initWithInterfaceName:] + 120

3 SymptomEvaluator 0x00007fff86915918 config_callback + 874

4 SystemConfiguration 0x00007fff98cc2fbf rlsPerform + 184

5 SystemConfiguration 0x00007fff98cd63bb __SCDynamicStoreSetDispatchQueue_block_invoke_2 + 52

6 libdispatch.dylib 0x00007fff877ae871 _dispatch_call_block_and_release + 12

7 libdispatch.dylib 0x00007fff877a333f _dispatch_client_callout + 8

8 libdispatch.dylib 0x00007fff877a7f6f _dispatch_queue_drain + 754

9 libdispatch.dylib 0x00007fff877ae63b _dispatch_queue_invoke + 549

10 libdispatch.dylib 0x00007fff877a6c87 _dispatch_root_queue_drain + 538

11 libdispatch.dylib 0x00007fff877a6a34 _dispatch_worker_thread3 + 91

12 libsystem_pthread.dylib 0x00007fff8e4b268f _pthread_wqthread + 1129

13 libsystem_pthread.dylib 0x00007fff8e4b0365 start_wqthread + 13

Feb 5 23:34:10 mymacmini symptomsd[224]: -[NWInterface initWithInterfaceName:] nw_interface_create_with_name(iptap0) failed, dumping backtrace:

[x86_64] libnetcore-583.20.10

0 libsystem_network.dylib 0x00007fff928a6ba5 __nw_create_backtrace_string + 123

1 Network 0x00007fff91850096 -[NWInterface initWithInterfaceName:] + 226

2 SymptomEvaluator 0x00007fff86915918 config_callback + 874

3 SystemConfiguration 0x00007fff98cc2fbf rlsPerform + 184

4 SystemConfiguration 0x00007fff98cd63bb __SCDynamicStoreSetDispatchQueue_block_invoke_2 + 52

5 libdispatch.dylib 0x00007fff877ae871 _dispatch_call_block_and_release + 12

6 libdispatch.dylib 0x00007fff877a333f _dispatch_client_callout + 8

7 libdispatch.dylib 0x00007fff877a7f6f _dispatch_queue_drain + 754

8 libdispatch.dylib 0x00007fff877ae63b _dispatch_queue_invoke + 549

9 libdispatch.dylib 0x00007fff877a6c87 _dispatch_root_queue_drain + 538

10 libdispatch.dylib 0x00007fff877a6a34 _dispatch_worker_thread3 + 91

11 libsystem_pthread.dylib 0x00007fff8e4b268f _pthread_wqthread + 1129

12 libsystem_pthread.dylib 0x00007fff8e4b0365 start_wqthread + 13