Letting linux be the router, allowing dynamic routes, suggestion

Marcelo Pacheco marcelo at m2j.com.br
Tue May 12 22:21:49 CEST 2015


I see what you want me to do. But it does incur an extra MAC layer header
to each VPN packet, more fragmentation.
And broadcasts leak to all peers.
It sure saves you from doing any improvements, but there are side effects
that are undesirable to many customers.
This is specially a problem if I want two VPN connections between two sites
using redundant connections, we get an instant L2 loop.
With my proposal this doesn`t happen since the traffic between peers is
still L3.

On Tue, May 12, 2015 at 4:45 PM, Guus Sliepen <guus at tinc-vpn.org> wrote:

> On Tue, May 12, 2015 at 04:27:10PM -0300, Marcelo Pacheco wrote:
>
> > Consider the challenge of having completely dynamic routing between vpn
> > peers. In one minute I might have 10000 routes towards one specific peer,
> > and hour latter I might have NONE. And I need to diferentiate each peer
> at
> > the kernel routing layer.
> > And no, it can't be a pure bridge, it has to be L3 routing.
>
> Although the manual says that switch mode is primarily useful for
> bridging Ethernet segments, it doesn't say you cannot use it for other
> things, including what you want.
>
> In switch mode, tinc routes solely based on the Ethernet header.
> Whatever you want to do with that is up to you. If you want to add or
> remove 10000 routes to a specific node, then just add those routes with
> the gateway address set to that node. If you want to run OSPF or any
> other routing protocol on top of tinc, that is possible as well.
>
> > Instead of creating a heap of tun devices, there's a more logical
> > solution. Create a TAP device, and emulate ARP on the VPN software.
> > The many peers would form a virtual ethernet device, where each tunnel
> > has a separate virtual MAC address.
>
> That is already exactly what happens in switch mode; tinc creates a tap
> interface and forms a virtual switch. It doesn't have to emulate ARP at
> all, the kernel will generate ARP packets as usual. Each node's tap
> interface has its own MAC address.
>
> --
> Met vriendelijke groet / with kind regards,
>      Guus Sliepen <guus at tinc-vpn.org>
>
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