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Stack Exchange
Stack Exchange
1:36 PM
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Q: PPTP VPN connected but cannot open webpage with Mac

John WangI've setup a PPTPD on my VPS(Debian) which I used to use very well from my android phone and windows laptop. Now I want my new Mac Mini to use it too. It's shown the Mac can establish the vpn connection, only the browser(or curl) cannot open any webpages. What's the problem? BTW, I'm accessing ...

vpn mac pptp
 
NickW
NickW
What sort of error does it give you? Have you tried to see if pings work, to see if it is connectivity in general, or just a web issue?
 
John Wang
John Wang
ping works. I just updated my question.
 
NickW
NickW
I'd have a look at your MTU settings on the mac. Looks like a classic case of packets getting fragmented, but not being re-assembled, or worse, dropped by firewalls.
 
John Wang
John Wang
how to see the MTU settings ?
 
NickW
NickW
System Preferences > Network > [your connection] > Advanced... > Hardware > Configure: {Manually,Automatically}
 
John Wang
John Wang
1:36 PM
Yes, it's 1500 in "Automatically"
Thank you Nick. this issue stucked me for weeks!
BTW, I've never used Talk here before ;-)
 
NickW
NickW
No problems, is this the VPN connection or the Ethernet ?
yeah, it's pretty cool
 
John Wang
John Wang
currently it's ethernet
 
NickW
NickW
so it's the one that becomes the VPN, right?
 
John Wang
John Wang
I'm unfortunately behind the GFW,i.e., in China
yes
it's the one one which VPN goes
on which VPN goes
 
NickW
NickW
OK, we're going to drop it down to too low a number, just to see if it works
set it to 1400
then try and connect
 
John Wang
John Wang
1:42 PM
ok
 
NickW
NickW
I'll chill here in the meantime :)
 
John Wang
John Wang
Actually, I dont know what chill means(my poor english), but, haha ...
 
NickW
NickW
ah, it means relax :)
 
John Wang
John Wang
now I changed it to 1400
should I try my VPN connection now ?
 
NickW
NickW
Yeah, give it a go
 
John Wang
John Wang
1:47 PM
My God!
It's really that simple !
Done !
Weeks of pains !
 
NickW
NickW
yeah, now you need to test how high you can get it before it stops working
 
John Wang
John Wang
Thank you so much
 
NickW
NickW
give 1472 a go
when you have time :)
 
John Wang
John Wang
sure
you mean the higher the better ? performance ?
 
NickW
NickW
Yeah, basically the MTU is the maximum amount of "stuff" that each packet can hold
too high and it gets fragmented.. too low and you send more packets
so there is a sweet spot in the middle
anyhow, it's a long process to explain
 
John Wang
John Wang
1:51 PM
At least it's already a good lession for me. Thank you so much !
 
NickW
NickW
BTW, if 1472 works, try 1473, etc, you want to get as close to 1500 as possible
not a problem
 
John Wang
John Wang
could you give a fomal answer so that I can accept it
a formal answer to my question
 
NickW
NickW
I'm gonna go write up the answer, so if anyone else has the same problem..
yeah, off to do that now
see you around!
 
John Wang
John Wang
sure, see you. thank you again ;-)
 

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