tinc and routing

[Clark Rawlins]

After talking to Guus offline the answer is to let tinc know it
needs to handle packets for additional networks.

In the host file (on each machine in the vpn) 
Adding an additional Subnet line

Subnet = 172.16.1.0/24 

lets tinc know to route packets for that network to that host.

Clark



> -----Original Message-----
> From: Guus Sliepen [mailto:guus at sliepen.eu.org]
> Sent: Friday, October 10, 2003 10:37 AM
> To: tinc-devel at nl.linux.org
> Cc: Clark Rawlins
> Subject: Re: tinc and routing
> 
> 
> On Fri, Oct 10, 2003 at 09:46:31AM -0500, Clark Rawlins wrote:
> 
> > I'll try that but to clear up an apparent misunderstanding:
> > The 192.168.9.1 machine is multi-homed with 172.16.1.1 so they
> > are the same machine.
> 
> Ah okay, that explains why IndirectData doesn't have any effect :)
> 
> > What I had hoped would happen is that traffic from 192.168.0.0/24 
> > headed for 172.16.1.0/24 would be routed via the vnc device to the 
> > gateway specified for 172.16.1.0/24 which is 192.168.9.1 from there
> > the traffic would be routed to the eth2 interface which is the local
> > subnet on the multi-homed host 192.168.9.1 - 172.16.1.1 and 
> from there 
> > to its final destination.
> 
> Hm. Could you send me your tinc-up scripts and the configuration files
> in the hosts/ directory?
> 
> > This doesn't seem to happen for some reason.
> > You said that the gateway router gets ignored by either the 
> kernel or 
> > by the tinc daemon?  My understanding (which may be flawed) 
> was that for
> [...]
> > Once it has the hardware address for the gateway address it 
> sends the packet
> > to the gateway address as an ethernet unicast message.
> 
> Correct.
> 
> > I don't know how this compares to what tinc does perhaps 
> > you could enlighten me?
> 
> Why the kernel would ignore the gateway address:
> 
> If you use tinc 1.0 or later and the universal tun/tap device from the
> Linux kernel, tinc will use that device in tun mode, which means it is
> not an Ethernet interface, but a pure IP interface. In that 
> case, there
> are no Ethernet addresses involved, and the gateway address 
> is not used
> at all by the kernel.
> 
> Why tinc would "ignore" the gateway address:
> 
> Well in router mode, tinc can only route IPv4 and IPv6 packets. ARP is
> not an IPv4 protocol, it is something Ethernet specific. It does not
> forward broadcast ARP requests to all other tinc daemons in the VPN.
> However, tinc has built-in proxy-arp that will fake replies 
> for ARP requests it
> receives on the virtual network device. If you specify a 
> gateway address
> for the route, then the kernel will send ARP requests for that gateway
> address. If you omit it, then the kernel will send ARP 
> requests for the
> destination address of the packets you send. Tinc responds to both
> requests, the kernel is happy because it now knows an 
> Ethernet address,
> sends it to the virtual network device, and tinc will route 
> the packets
> to the correct destination tincd (without looking at the Ethernet
> address, just at the IP addresses in the packets).
> 
> -- 
> Met vriendelijke groet / with kind regards,
>     Guus Sliepen <guus at sliepen.eu.org>
> 
--
TINC development list, tinc-devel at nl.linux.org
Archive: http://mail.nl.linux.org/tinc-devel/