Windows subnets

Thu Oct 7 02:13:23 CEST 2010

Sorry you're right.  I was looking at the IP address schema where all nodes
would use the 10.30.0.0/24 network.

There's no need to install tap adapters on the other devices.  You have
basically 2 realistic options if you want the LAN function

You can specify multiple IP addresses for a single interface, even in
Windows.  You'll find this under the TCP/IP properties of the network
adapter.  And clicking on the Advanced button on the page where you can set
a static IP or designate DHCP.

A 2nd option would be to re-ip one of your locations so that they all use
the same subnet natively.

Bridging the tap adapter allows your network frames received by your
physical interface to reach the TAP adapter and therefore traverse the VPN.
This enables later 2 connectivity, the same way a real switch does.  Virtual
Ethernet over the Internet is how I like to describe it.  This is how I have
my VPN configured personally.

Without the bridge, a frame that is received at the physical interface has
the frame stripped off and the packet inspected.  Now we're talking layer
3.  If the packet is destined for a network on the other side of the VPN,
your Tinc node frames the packet back up with a new frame, and sends it over
the VPN.   This act of stripping the frame, reading the packet for the
network destination, and applying a new frame to get it there is what
Routing is.  Without the bridge in place, your Tinc node is literally
routing between the physical interface and the tap interface.  With the
bridge, you're creating a layer 2 pathway so the frames can shoot across
directly.  Of course this means both sides need to be on the same subnet
which you obviously already know.

Be warned that this configuration comes with it's drawbacks.  DHCP will
traverse your VPN.  I had location A computers getting addresses from
location B which makes for some really inefficient internet traffic.

Regards,
Donald
On Wed, Oct 6, 2010 at 7:57 PM, Andrew Savinykh <andrews at brutsoft.com>wrote:

>  Donald, thank you for the explanation.
>
> I understand the part about the switch mode and absence of subnet in
> tinc.config.
> However, could you please explain what bridging the tap adapter will
> achieve and what kind of ip address will be used on tinc nodes and in the
> rest of the network.
>
> In my example one household has local network addresses of 192.168.1.* and
> the other has 10.1.1.*
> If we don't install tap interfaces on other PC's this means that the other
> PCs won't have another ip address.
> I understand that bridging is going to solve this somehow, but I still
> don't see how broadcast from 10.1.1.7 can reach 192.168.1.5 in the other
> LAN.
>
> In short I don't understand how bridging to adapters work. I'll try to
> google this topic to get a better understanding, meanwhile, could you please
> explain
> how this applies to our tinc configuration case.
>
> Also can you briefly describe what we achieve by setting PMTUDiscovery =
> Yes. I read the description in manual but it didn't tell me much.
>
> Thank you again for all your help,
> Andrew
>
>
>
>
> On 7/10/2010 11:40 a.m., Donald Pearson wrote:
>
> Oh okay.  Yes you can make it appear as a single LAN.  Your Tinc nodes will
> behave as bridges instead of routers (or gateways as you put it).
>
> Your tinc nodes will have the same subnet mask and default router as all
> your other devices at that location.
>
> You will need to run the add-tap script only on the tinc nodes on each
> side.
>
> You will then need to bridge the tap adapter to the local area connection
> on the tinc nodes on each side.
>
> This will create a bridge network object under your network connections.
> This bridge will have the IP configuration you illustrated.
>
> You have the right idea in segregating the IP distribution while still
> using the 255.255.255.0 subnet mask.
>
> One both nodes are up and connected, and the interfaces have been bridged
> on the Tinc nodes for each location, you will have a virtual LAN between the
> two locations.
>
> Your Tinc configuration will be Switch mode.   This means no Subnet
> configurations are required in your tinc.conf
>
> Your tinc.conf will be something like
>
> Name = NodeA
> ConnectTo = NodeB
> Interface = <something>
> Mode = switch
> PrivateKeyFile = <path to the rsa_key.priv>
>
> Host files will be something like
> For the host file named "NodeA"
>
> Address = <host.dyndns.org>
> PMTUDiscovery = Yes
>
> --Begin RSA etc. etc.--
>
>
> On Wed, Oct 6, 2010 at 6:17 PM, Andrew Savinykh <andrews at brutsoft.com>wrote:
>
>>  Donald,
>>
>> thank you, while I still have some questions, your answer is definitely a
>> step in the right direction.
>> In the other reply I was asked what I'm trying to achieve. Let's consider
>> the following scenario (which is quite similar to the one that described in
>> the tinc manual).
>>
>> Let's assume we have two households, each has 3-5 computers in it.  Both
>> house holds have similar network configuration:
>> They are connected to internet with an ADSL line and a router.
>> The computers in the local network access internet via the router.
>> The router is configured so that one of the computers have port 665
>> forwarded to be accessible outside.
>> The external IP is changed rarely and there is dynamic DNS service
>> (external) in use to accommodate for the change of IP when it happens.
>>
>> One household has local network addresses of 192.168.1.* and the other has
>> 10.1.1.*
>> I'm installing tinc on one computer in each household.
>>
>> The goal is to let all computers in both house holds to see each other by
>> ip address. Also it is desired that for computer games purposes
>> all computers appear to be on the same LAN (for broadcasts). But this is
>> not mandatory. (it appears that it's not possible without installing tinc on
>> every PC
>> as every tinc daemon serves a subnet and two tinc daemons can't serve a
>> part of subnet each)
>>
>> All computers run different flavours of Windows, most being Windows 7.
>>
>> I have two ideas how to set this up, although I'm not sure if any of these
>> two works:
>>
>> IDEA1.
>> =====
>> Household A
>> Gateway IP: 10.30.0.1
>> Gateway Mask: 255.255.255.0
>> Gateway Default Gateway: ????
>>
>> Other PCs IP: 10.30.0.2,3,4 etc
>> Other PCs Mask: 255.255.255.0
>> Other PCs Deafult Gateway: 10.30.0.1
>>
>> Tinc Subnet: 10.30.0.0/25
>>
>> Household B
>> Gateway IP: 10.30.0.129
>> Gateway Mask: 255.255.255.0
>> Gateway Default Gateway: ????
>>
>> Other PCs IP: 10.30.0.130,131,132 etc
>> Other PCs Mask: 255.255.255.0
>> Other PCs Default Gateway: 10.30.0.129
>>
>> Tinc Subnet: 10.30.0.128/25
>>
>>
>> IDEA2.
>> =====
>> Household A
>> Gatway IP: 10.30.0.1
>> Gateway Mask: 255.255.255.0
>> Gateway Default Gateway: ????
>>
>> Other PCs IP: 10.30.0.2-255 etc
>> Other PCs Mask: 255.255.255.0
>> Other PCs Default Gateway: 10.30.0.1
>>
>> Tinc Subnet: 10.30.0.0/24
>>
>> Household B
>> Gateway IP: 10.30.1.1
>> Gateway Mask: 255.255.255.0
>> Gateway Default Gateway: ????
>>
>> Other PCs IP: 10.30.1.2-255 etc
>> Other PCs Mask: 255.255.255.0
>> Other PCs Default Gateway: 10.30.0.129
>>
>> Tinc Subnet: 10.30.1.0/24
>>
>>
>> So IDEA 1 probably won't work at all. Will it? And with IDEA 2 the pc's
>> won't appear on the same LAN and their broadcasts won't reach each other.
>> As far as I understand I need to install TAP interface on each of the
>> participating windows PCs, correct?
>> What is specified in default gateway of the gateways?
>>
>>
>>
>> Thank you in advance,
>> Andrew
>>
>>   On 7/10/2010 4:36 a.m., Donald Pearson wrote:
>>
>>  The PCs that you want to participate need to have a route for the VPN
>> subnet pointing to their local VPN gateway, which would be the local device
>> with Tinc installed on it.
>>
>>  Theoretical configuration example.
>>
>>  VPN subnet is 10.10.10.0/24
>>
>>  At a location, one computer 192.168.1.254/24 connects to the VPN and
>> serves as the VPN gateway.  This gateway needs to be configured for TCP/IP
>> forwarding.
>>
>>  http://support.microsoft.com/kb/315236 - windows
>> http://www.ducea.com/2006/08/01/how-to-enable-ip-forwarding-in-linux/ -
>> linux
>>
>>  Other computers local to the gateway need a route to the VPN network
>> added so they know how to get there.
>>
>>  In windows.   route -p add 10.10.10.0 mask 255.255.255.0 192.168.1.254
>> This will add the persistent route that remains after reboot.
>>
>>  Does that answer your question?
>>
>> On Wed, Oct 6, 2010 at 6:41 AM, Andrew Savinykh <andrews at brutsoft.com>wrote:
>>
>>>  Thank you for your reply. As far as I can see there is no point
>>> specifying subnet that consists of more than one PC in tinc config if you
>>> are going to install tinc on every PC in the subnet anyway. Correct me if
>>> I'm wrong.
>>> Now, assuming I'm right, there will be PCs in the subnet that don't have
>>> tinc installed on them. How to configure these PCs so they are a part of the
>>> subnet and participate in routing?
>>>
>>> Cheers,
>>> Andrew
>>>
>>>
>>> On 6/10/2010 10:13 p.m., Cédric Lemarchand wrote:
>>>
>>>  Hi,
>>>
>>> I am not sure to understand what you mean with "joining" a subnet.
>>>
>>> But if your "local computer" need to reach the "remote subnet" served by
>>> tinc, you can set the local IP of the local tinc server as the default
>>> gateway, or add a route to the remote subnet via the local tinc IP. Of
>>> course, computer located on the remote subnet need the same thing.
>>>
>>> Cédric
>>>
>>> Le 06/10/10 09:37, Andrew Savinykh a écrit :
>>>
>>>  Hello all,
>>>
>>> I understand that each tinc daemon corresponds to one or more subnets
>>> that it "owns" a subnet can be a single ip or more.
>>> Could you please tell me what do I need to do to join a computer in local
>>> network (windows) to a subnet served by tinc?
>>>
>>> Thank you in advance,
>>> Andrew
>>>
>>>
>
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