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Bridge two Separate Subnets with wireless DD-WRT

Posted on 2013-01-30
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Last Modified: 2013-02-05
Hey everyone.  I need a little help.

I have two separate networks (Network A 192.168.62.x, Network B 192.168.63.x both subnetmask 255.255.255.0) and I need to setup a wireless bridge between both of them without changing the subnet info.  Both location currently have dd-WRT routers as the primary router in place for internet and DHCP.

I have TWO extra DD-WRT Wireless routers (Linksys WRT54GL) to use as access points for testing, I'd like to get some routers with DD-WRT capable of doing 802.11N after I figure this out.

I've read a bunch about doing standard bridging with these routers and did get a standard bridge setup but was unable to get the routing between the two subnets worked out. Plus I think the setup should be totally different from what I did to get the standard client bridge working.

So with a total of 4 DDWRT Routers (right now all WRT54GL, 2 used as standard routers with LAN Subnets listed above and the Router lan IP's being 192.168.x.1) how can I set this up?
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Question by:N3admin
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by:agonza07
agonza07 earned 200 total points
ID: 38838415
Not sure if this will work, but theoretically it should.

Configure routing on both routers. Its should be under the advanced routing tab. Configure both main routers as routers (RIP or OSPF, it doesnt matter since you won't be using either protocol, just static.)

Set up your bridging routers as a standard bridge. THis part you already did it sounds like.

On the routers, let's say the IP addresses are:
192.168.62.1 and 192.168.63.1

You need to create secondary IPs for both units using the link below.
http://randomerror.wordpress.com/2010/01/13/adding-an-ip-alias-on-dd-wrt/
On 192.168.62.1 create 192.168.63.2
On 192.168.63.1 create 192.168.62.2

Then configure static routes.

On 192.168.62.1 configure a static route as follows:
Destination LAN: 192.168.63.0
Mask: 255.255.255.0
gateway: 192.168.62.2

On 192.168.63.1 configure a static route as follows:
Destination LAN: 192.168.62.0
Mask: 255.255.255.0
gateway: 192.168.63.2

The problem with this is that DHCP requests may cross the bridge, but at least I got you thinking.

Use this guide to help you configure a third LAN just for your bridge and then use the steps above to configure the routing.
http://geek.co.il/wp/2007/06/11/setting-up-dmz-with-multiple-static-ips-on-an-office-lan-using-dd-wrt
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by:N3admin
ID: 38841171
Sweet, I'll give this a try today and report back.   Thanks for the time!  I also have another idea I'll be trying out today as well.

I'm pretty shocked how little info there is out there regarding this sort of situation.
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N3admin earned 0 total points
ID: 38842076
agonza07 thank you for chiming in on this. I believe your solution may work but I didn't have a chance to try it today.  The you indicated there may be a problem with DHCP with that setup and I can see why since there is no true routing going between the two Subnets. This could cause major issues so I decided to try and do something with routing between.

Okay, I've got it all setup and here is how I accomplished it.
First I setup a standard wireless bridge using this "How-to" from the primary network (lets call it Network A)
http://www.youtube.com/watch?v=vS-Jk-v0Aaw

This created a switch (on Network A) at then secondary location providing a wireless link to the primary location.
Then I setup one of the DD-WRT routers in ROUTING MODE shown here:
http://www.dd-wrt.com/wiki/index.php/Linking_Subnets_with_Static_Routes

This provided a stable link between the two subnets. I could ping everything from network B to network A, however pings were not working from Network A to network B.  I checked all the firewall information I could and had all the firewall stuff off on the middle router doing the routing between subnets. I even added the allow all script to the firewall (iptables -I FORWARD -j ACCEPT), but alas it didn't seem to allow pinging though.

I WAS however able to pull up shared folders from each side. Both sides have DHCP working on their own network and Internet is kept separate at each location as well.

This was all done in a lab environment with 3 LINKSYS WRT54GL routers with DD-WRT SP1 and 1 Asus RT-N12 with DD-WRT SP2 on it.  With the wireless bridge about 15ft away and the routers set to WiFi G only and a few tweaks I was able to get about 2.3-2.5 Megabytes a second out of the wireless bridge.  The tweaks in the advanced WiFi I setup for this config are:
Frame Burst: Enabled (This is Linksys SpeedBooster!)
Beacon Interval: 80 (down from 100, to help avoid connection drops)
Max Associated Clients: 40 (I don't need 128 clients in this case)
Preamble: Short
Shortslot override: Short
Afterburner: Enabled (This can help boost speed with Wireless G when enabled, but unfortunately will lock N clients to 54 Mbps for some reason...do NOT Enable it unless you're only on WiFi G)

In the field I Plan on using a more robust outdoor Wireless Bridge/AP setup using 802.11N to help improve bandwidth. I'll continue to use dd-WRT for the routing, most likely the trusty ole' WRT54GL's I always have a few of.
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by:N3admin
ID: 38842158
upon further checking of this lab setup I'm able to ping through both networks as long as I'm not pinging over the wireless bridge.  It appears that the wireless bridge is causing some routing issues.  I'm not sure if this is DD-WRT related or not, I'm going to purchase a couple wireless bridges and test it out further.
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by:N3admin
ID: 38844717
Here is a diagram of the lab test I did.  The IP's don't match up from the first post, but that's due to working in the lab and just doing testing.
Google doc link of the diagram
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Author Closing Comment

by:N3admin
ID: 38854340
As this works, it doesn't appear to be perfect routing between subnets since I was only able to ping it's from side of the network. However I was able to access shared folders on each side of the network regardless.
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by:N3admin
ID: 38857698
Okay, replacing the DD-WRT routers with real Wireless Bridges (I used Engenius ENH202 model) I was able to get things working properly with regards to routing and pinging through a single DD-WRT Router to handle the routing between subnets.
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