VPN issue: Same subnet at home as at work, works on Win but not OSX?

Question

VPN issue: Same subnet at home as at work, works on Win but not OSX?

We have a VPN server that resides on the 192.168.1.0/24 network here at work. Yes, it is stupid, but this was inherited and no time to change.

I have a coworker who needs to access the VPN from her home network. Her home router is also using the 192.168.1.0/24 private subnet.

She claims she can connect but cannot access any work resources over the VPN, so I tried it at home and set my network to 192.168.1.0/24 and she is correct when I try from my iMac. (She is using a MacBook)

When I do the same thing with my Windows 7 machine, it connects and I can access resources without any trouble.

The Mac is attempting to access stuff on the local 192.168.1.0/24 network rather than the remote one. Why is this different between the two platforms?

In my research, the only conclusions have been MrHoffman saying to change the subnet at work. That is not possible. Other suggestions are to have the user change their network at home. This user is not very savvy and does not know how to do this. I also feel this is a poor answer.

This situation is not a problem on a Windows workstation, however it is on OSX. I am determined to accomplish the same functionality on OSX as I get on Windows.

MacBook Pro, Mac OS X (10.6.6)

Posted on Mar 5, 2011 2:29 PM

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Answer 1

Mar 9, 2011 9:18 AM in response to DeusExMachinae

Tried changing the service order of my network devices to no avail.

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Answer 2

satcomer

Level 4

1,593 points

Mar 9, 2011 9:22 AM in response to DeusExMachinae

Are you telling the VPN client to only use data through the VPN connection?

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Answer 3

yomichee

Level 1

21 points

Mar 10, 2011 3:07 PM in response to satcomer

I have encountered this issue with XP era machines and VPN connection on same subnets. once connected no mail or internet etc. Haven't used VPN and Windows 7 yet so no experience to draw from.

You can have the client use a dis-similar network say the 10.0.0.0
or
employ VPN split tunnel on the VPN server to allow client access to internet

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Answer 4

yomichee

Level 1

21 points

Mar 10, 2011 3:19 PM in response to satcomer

Agreed ... try the allow all traffic through VPN selection in the advanced configs for the VPN connection

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Answer 5

Mar 24, 2011 8:52 AM in response to yomichee

I did try checking "Send all traffic" and that made no difference.

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Answer 6

Bugxo

Level 1

0 points

Jul 16, 2014 4:28 PM in response to DeusExMachinae

I have same problem. At home I have 192.168.2.0/24 subnet and at company we have the same 192.168.2.0/24. I want to access windows share server in company using PPTP VPN. As PPTP server there is Mikrotik. VPN connects fine, but when I want to access Windows share server on ip 192.168.2.240 in company, routing table on Mac OS X was set up to search it in local network on Wifi interface. The next commands helped me:

1. Set static arp entry for your local network gateway (my is 192.168.2.1 and is 0:c:42:dc:8d:55 on interface en0)

sudo arp -s 192.168.2.1 0:c:42:dc:8d:55 ifscope en0

This is necessary for accessing gateway, after you remove the local subnet route in next step.

2. Delete link route for your local network subnet (My is 192.168.2.0/24)

sudo route delete -net 192.168.2 -link

I have enabled "Send all traffic over VPN connection".

Routing table after modification: netstat -rn

default 192.168.2.254 UGSc 5 6 ppp0 - created by "Send all traffic over VPN connection" default 192.168.2.1 UGScI 0 0 en0 127 127.0.0.1 UCS 0 0 lo0 127.0.0.1 127.0.0.1 UH 3 6123047 lo0 169.254 link#4 UCS 0 0 en0 192.168.2.1 0:c:42:dc:8d:55 UHLSI 1 2 en0 192.168.2.10 127.0.0.1 UHS 0 0 lo0 192.168.2.254 192.168.2.199 UHr 15 99 ppp0 213.151.238.31 192.168.2.1 UGHS 2 4419 en0

Arp table after modification: arp -an

? (192.168.2.1) at 0:c:42:dc:8d:55 on en0 ifscope permanent [ethernet]

I did not try to write script to run these commands automatically. This question is pretty old, if somebody has another solution, please share 🙂

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Answer 7

Aug 31, 2014 7:20 AM in response to Bugxo

This solution worked perfectly on Mavericks in the same situation. Thanks for sharing!

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