Seeing computers in seperate subnets in "Network" view.

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Fellhahn
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Seeing computers in seperate subnets in "Network" view.

Post by Fellhahn » 19 Apr 2009, 10:33

Situation: Me and a mate (Kaan for those with very long memories) have set up a LAN to LAN VPN between our routers, I'm using a Billion 7404VGO and he's using a 7402VGO, for the purpose of sharing media. So far we've got the tunnel working correctly, we're using PPTP, and after making some adjustments in Windows firewall we can navigate to each others machines when we type IPs into the explorer address bar, from there we can see all shared media and copy and paste to our hearts content.

Objective: What we still can't get to happen is when we open up the "Network" view, we still only see machines on our local subnets. I'm on a x.x.1.0/24, he's x.x.2.0/24, the LAN to LAN VPN requires the two connecting networks be on separate subnets. We want all the machines to appear in Network, or My Network Places as it was back in Xp. All the machines involved (there's about 6) are running Vista ultimate, mixture of x64 and x86.

So far I've been working with "Windows firewall with advanced security", I adjusted some of the inbound rules and added the x.x.2.0 subnet to the permitted remote addresses for various functions. This is what got the basic file sharing working however I've made the same adjustment to several other rules that I thought would deal with the Network view and so far no good.

Question: Is what I'm trying to do even really possible? I've found one reference that claims the Network discovery is layer 2 based, which means it wouldn't work beyond our routers. However I've only found the one reference for this, and it didn't seem too reliable.

If anyone's got any experience or advice on this please share.

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Re: Seeing computers in seperate subnets in "Network" view.

Post by Messer » 20 Apr 2009, 02:17

I have never done any VPN networkng, but I would suggest temporarily disabling your internet security programs (firewall, internet security packages) on both computers to rule out configuration problems on either end, if it works then something is not set up right, if it doesent mebbe try re-installing XP PRO :) jokes.

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Re: Seeing computers in seperate subnets in "Network" view.

Post by Silurin » 20 Apr 2009, 07:44

I think the network discovery used with browsing like you want to do is a broadcast protocol and by default it doesn't function beyond a router/local subnet to prevent network traffic being flooded with these discovery messages and killing what is typically a slow WAN link (compared to the LAN itself). I don't know that the Billion routers have the capability to allow that traffic through them (I'll check my 7404 later), but one option may be to install a program which builds the network picture for you, something like this may help
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Re: Seeing computers in seperate subnets in "Network" view.

Post by nitrofenix » 20 Apr 2009, 09:09

What VPN software are you using?
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Re: Seeing computers in seperate subnets in "Network" view.

Post by Fellhahn » 20 Apr 2009, 20:24

The VPN function is built into the routers, they act as the endpoints.

Edit: Also Hi-Five for 7404 boyz :P
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Re: Seeing computers in seperate subnets in "Network" view.

Post by Spyder » 20 Apr 2009, 21:57

7402G ftw! :P

Everyone else got really close, but this isn't a router configuration issue. It's a "welcome to low level windows networking" issue. The normal answer is that cross-subnet windows networking requires a WINS (Windows Internet Name Server). Funnily enough Microsoft only built WINS technology into the Windows Server OSs which is pricey, or Samba also supports it (but if you don't know linux that could be tough to set up). Luckily, there's an easy answer in this case.


There is no physical barrier separating your two subnets; Billion VPN just blindly forwards appropriate packets (i.e. you can access each other by IP). What this means is you don't need a WINS server - you just need to open up your subnet mask. I run multi subnet at home; 10.4.1.* and 10.4.2.* are servers, 10.4.10.* are my desktop machines / iPhone and 10.4.69.* is what the DHCP server gives out for guests. 10.4.19.* is one flatmate, 10.4.40.* is the other... you get the idea.

To make that work, instead of using subnet mask 255.255.255.0 change it to 255.255.0.0. if you don't want to break your head with low-level networking detail you can stop reading right here and have fun with your network ;)


Still with me? If you look at the numbers from a funny angle it should be fairly obvious why this fixes it. The subnet mask determines who you broadcast to using a bitmask. IPV4 addresses are broken up into 4 "classes" - A.B.C.D. The default subnet mask that most people use is a D-class broadcast, by setting the C class to 0 you're now broadcasting to both C and D class networks.

There is some fancy math involved to only broadcast to a handful of IPs in each class, but for home networking all you need to know is that each segment set to 255 won't get broadcast messages but each segment set to 0 will. By setting the third segment to 0 your broadcast messages will be available to all C class networks - so "find all machines on the network" messages from x.x.2.0 will be picked up by x.x.1.0 and vice versa.


... I'm sure the real networking gurus (/hug nucleon) will pick holes in that explanation but it's close enough ;)
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Re: Seeing computers in seperate subnets in "Network" view.

Post by Fellhahn » 20 Apr 2009, 22:33

I think I should be able to understand this, but not this close to bedtime :P

Thanks Spyder, I'll come back to this tomorrow.
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Re: Seeing computers in seperate subnets in "Network" view.

Post by nitrofenix » 20 Apr 2009, 23:00

Spyder wrote:instead of using subnet mask 255.255.255.0 change it to 255.255.0.0
..
There is some fancy math involved to only broadcast to a handful of IPs in each class, but for home networking all you need to know is that each segment set to 255 won't get broadcast messages but each segment set to 0 will. By setting the third segment to 0 your broadcast messages will be available to all C class networks - so "find all machines on the network" messages from x.x.2.0 will be picked up by x.x.1.0 and vice versa.
Aye, this is pretty much what I was going to suggest.

As far as network subnet masks go, 255.255.0.0 will do the trick, but if you're looking to tighten things up, setting it to 255.255.252.0 should be enough to pick up xxx.xxx.0.1 ~ xxx.xxx.3.254, which, after reading the OP, sounds like it should also do the trick.
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Re: Seeing computers in seperate subnets in "Network" view.

Post by Spyder » 20 Apr 2009, 23:06

But why would you bother when there are no other broadcast packets to filter out with such a small network - leaving it at 0 is much easier to explain ;)
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Re: Seeing computers in seperate subnets in "Network" view.

Post by nitrofenix » 20 Apr 2009, 23:07

Haha, I've done amateur tech support long enough to know that some home networks can be srs bsns. :lol:
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Re: Seeing computers in seperate subnets in "Network" view.

Post by nucleon » 24 Apr 2009, 19:52

Spyder wrote: ... I'm sure the real networking gurus (/hug nucleon) will pick holes in that explanation but it's close enough ;)
Woohoo I got a hug from Spyder :)

yeah all good. For those studying networking... The 'old skool' IPv4 class system is broken down to:

Code: Select all

Class    IP Range                      Netmask associated with class
Class A: 0.0.0.0   - 127.255.255.255   255.0.0.0
Class B: 128.0.0.0 - 191.255.255.255   255.255.0.0
Class C: 192.0.0.0 - 223.255.255.255   255.255.255.0
Class D: 224.0.0.0 - 239.255.255.255   -
Class E: 240.0.0.0 - 255.255.255.255   -
Class D - multicast address space, allocated individually not allocated to subnets (so no netmask associated with them). Class E - originally classed as reserved, there's movements to regarded this range as "Limited Use for Large Private Internets".

Nowadays - this isn't what's done in practice as IPv4 space is 'tight'. Recently APNIC released a 'class A' network to different organisations as much smaller subnets. I digress, back to the problem...

The theory -

To have a machine listed under networking neighborhood etc.... Windows sends a netbeui broadcast (255.255.255.255 and also the local subnet broadcast i.e. 192.168.1.255 for 192.168.1.0/24) asking "who's there?"

Routers do not forward broadcasts away from the local subnet by default.

Now, for the other side to see it, the routers must forward broadcasts. I know how to do this on cisco kit (IOS routers and Cisco concentrators). I don't now if the routers above can do so. You will need to check the doco of the routers if you can do so.

Practice -

Changing the netmasks on the routers/window PCs is unlikely to assist - but hey it's something to try.

What could be done is to create an _additional_ tunnel between the two PCs. Using the source/destination IP addresses of the local private subnets. This creates a virtual network linking both PCs to a single subnet - hence broadcasts can be shared between them.

I believe in windows you can setup a PPTP/L2TP tunnel within windows - but you'd have to play around with it. I don't know MS networking to that level to give you exact steps to set it up.

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