Re: ppp / open vpn

[tony.chamberlain@lemko.com]

So how do I set up the ptp instead of topology mode?
Is that ethernet bridging, which was the only option I saw?
Or do I even want to change from topology?

-----Original Message-----
From: Jan Just Keijser [mailto:jan.just.keijser@gmail.com]
Sent: Wednesday, January 12, 2011 07:47 PM
To: 'James Carlson'
Cc: tony.chamberlain@lemko.com, linux-ppp@vger.kernel.org
Subject: Re: ppp / open vpn

James Carlson wrote:
> On 01/12/11 16:17, Jan Just Keijser wrote:
>   
>> James Carlson wrote:
>>     
>>> The whole point of a point-to-point interface (of any type; PPP, tunnel,
>>> or otherwise) is that it connects two distinct IP nodes.  Distinct.  Not
>>> one IP node to itself!
>>>
>>>   
>>>       
>> This is another trick of OpenVPN to assign "linear addresses" to clients
>> while using a PtP (tun) interface. It is enabled in OpenVPN 2.1 (and
>> openvpnas, which is based  on 2.1) by using the
>>  topology subnet
>> directive.
>>     
>
> That's simply frightening.  Thanks for the update; I had no idea anyone
> was relying on that sort of undocumented OS feature.
>
> Good luck getting a routing protocol to work reliably with that ...
>
>   
actually, this mode is not used in combination with routing protocols. 
'topology subnet' is used primarily when multiple clients are connecting 
to a single server. OpenVPN also support a "point-to-point" mode (for 
lack of a better term), which does follow the regular PtP semantics. 
Running a routing protocol in that mode is just as easy as running one 
over a ppp-based link.

HTH,

JJK