Building a Wireless Mesh Network

Modify By: Abner Ayala Acevedo and Luis Ñeco Original Author: Julio Castillo

Building a Wireless Mesh Network

I. INSTALL DD-WRT FIRMWARE INTO THE LINKSYS WRT54GL

ROUTER

The DD-WRT firmware provide us a lot more features than the original Linksys WRT54GL

router firmware.

To install DD-WRT firmware, we will need to download two firmware versions: mini and

standard. The mini version is due to some limitations imposed by the Linksys firmware where

you can only upload the firmware with a certain maximum size. This mini version doesn't have

OLSR, after flashing it to mini version we will need to flash it again with the standard version.

We will use v24-sp1 version.

IMPORTANT: Flashing the Linksys WRT54GL Router with DD-WRT will void the warranty.

Making a mistake flashing the device can render it unusable.

We will use the following hardware and software.

HARDWARE:

1. 02x Linksys WRT54GL wireless router

2. 02x Laptop

3. 02x Ethernet Cable

SOFTWARE:

1. Internet Explorer or Mozilla Firefox

2. dd-wrt.v24_mini_generic.bin

3. dd-wrt.v24_std_generic.bin

In addition, we will have to take the following precautions before install DD-RWT:

Disable all firewalls, anti-virus software, and wireless connections on the PC.

Do NOT use a wireless connection to upload firmware instead of it use a wired

connection.

Do NOT flash/backup your firmware over an https connection, use http.

Plug the blue Ethernet (Cat5/RJ45) cable that came with your router into the Network

Interface Card (NIC) on the back of your computer and into one of the ports labeled 1, 2,

3, or 4.

The “Internet” port on your router should be connected to your broadband source i.e.

cable or DSL modem.


1. Download the firmware images.

In order to upgrade the Linksys firmware, we have to go the next web site: http://www.dd-

wrt.com/site/support/router-database and download the two image files (Fig. 2).

Fig. 1: Linksys Router Model

Fig. 2: Image files to download

2. Restore to the Factory Defaults the router WRT54GL.

First, connect the PC to the WRT54GL via Ethernet cable (ports labeled 1-4, not the WAN or

Internet port). Then, open Internet Explorer and navigate to 192.168.1.1. This will open the

Linksys web interface and ask you for a user and a password. If you cannot remember them,

press the Reset button for 30 seconds, with this action the username and the password will be

reset to its original (username: admin & password: admin).

http://www.dd-wrt.com/site/support/router-database

http://www.dd-wrt.com/site/support/router-database


At the beginning we have the WRT54GL router with its original Linksys firmware (See Fig.

3).

Fig. 3: Original Linksys Firmware.

It is recommendable to restore the router to Factory Defaults, before flashing with another

firmware. (Fig. 4)

Go to Administration tab → Factory Defaults tab → Select "Yes".

Click the Save Settings button, and then OK.

http://sites.google.com/a/uprm.edu/ccli/Home/testbeds-1/wireless-mesh-network-testbed-using-wrt54gl-dd-wrt-and-olsr/image009.png?attredirects=0


Fig. 4: Restore to the Factory Defaults.

3. Upgrade the Linksys firmware to DD-WRT mini (File: dd-wrt.v24_mini_generic.bin)

Go to Administration Tab → Firmware Upgrade tab. Browse to the file dd-

wrt.v24_mini_generic.bin, and press the button Upgrade (Fig. 5). We will have installed DD-

WRT firmware mini edition.

Fig. 5: Upgrading to DD-WRT mini version.

4. Upgrade the Linksys firmware to DD-WRT Standard (File: dd-

wrt.v24_std_generic.bin)

Then, we have to do the same procedure as step 2 and 3, but in this opportunity we will




browse to the file dd-wrt.v24_std_generic.bin, and press the button Upgrade (Fig. 6). We will

have DD-WRT firmware Standard edition.

Fig. 6: Upgrading to DD-WRT Standard version.

II. SET UP A WIRELESS MESH NETWORK WITH OLSR

The Optimized Link State Routing Protocol (OLSR) is the most representative and popular

proactive routing protocol for Wireless Ad-Hoc networks. It has been developed at INRIA and

has been standardized at IETF as experimental RFC 3626 [2]. It uses Hello and Topology

Control (TC) messages to discover and then disseminate link state information throughout the

mobile ad-hoc network. Individual nodes use this topology information to compute next hop

destinations for all nodes in the network using shortest hop forwarding paths. Each router keeps

the topology information of the entire network, and where the routes to all other nodes are

always available, no matter whether there is any ongoing traffic or not.

We will use OLSR to set up a Wireless Mesh Network (WMN). We will need the following

requirements:



HARDWARE

1. Laptops (2)

2. Linksys WRT54GL Routers (2)

SOFTWARE

1. Windows

2. DD-WRT v24-sp1

3. Olsrd-0.5.6 ( http://olsr.org/releases/0.5/olsrd-0.5.6-r3-pre-cac1df64dcd5-setup.exe )

4. Wireshark-win32-1.2 (http://media-2.cacetech.com/wireshark/win32/wireshark-win32-

1.2.13.exe )

NETWORK TOPOLOGY

Fig. 7 depicts the configuration of the WMN with OLSR routing protocol.

Fig. 7: Wireless Mesh Network Topology.

2.1 ROUTERS CONFIGURATION

First, It is necessary to have installed DD-WRT v24-sp1firmware into the WRT54GL routers. If

it is not installed, go to Appendix A.

To enter to the routers's configuration. First, you have to use the Ethernet cable. Then, open a

browser and insert in it the IP Address of the router. By default it is 192.168.1.1 and the

username and the password are root and admin respectively. Then do the following actions to set

it up.

Go to Wireless tab → Basic Settings tab. Set the following parameters (Fig. 8).

Note: The IP Address field change depending of the number of router.

http://olsr.org/releases/0.5/olsrd-0.5.6-r3-pre-cac1df64dcd5-setup.exe

http://media-2.cacetech.com/wireshark/win32/wireshark-win32-1.2.13.exe


http://sites.google.com/a/uprm.edu/ccli/Home/testbeds-1/wireless-mesh-network-testbed-using-wrt54gl-dd-wrt-and-olsr/Topology.png?attredirects=0


Fig. 8: Set up the wireless interface.

The next time you enter to the router you can do it by 2 forms: With Ethernet cable or wirelessly.

If you choose the first one the IP of the router will be 192.168.1.1, but if you choose the second

one the IP of the router will be the new one you put in Fig. 7 that means 10.1.1.x.

For the second router you can chose 10.1.1.X where X can take values from 2 to 24

For your demo you could use:

Router 1: 10.1.1.1

Router 2: 10.1.1.3

Note: The SSID is the name of the network (like RUMNET), you can choose a unique SSID but

BOTH routers should have the same SSID.

Then, Go to Wireless tab → Wireless Security tab. Disable Security mode. This is done to make

this setup easier for troubleshooting (Fig. 9)



Fig. 9: Set the security mode disabled.

Go to Security tab → Firewall Tab. Disable SPI Firewall option. This is done to make this setup

easier for troubleshooting (Fig. 10)

Note: OLSR needs certain ports open to work and to simplify things we just disabled the firewall

instead. Later on if you want more security you can enable it and configure the iptables in the

router to let the needed ports open (OLSR uses port 698 UDP)

Fig. 10: Disable SPI Firewall for easiest setup for OLSR.

Finally, enable OLSR. Go to Setup tab → Advanced Routing tab. Choose OLSR Router in the

Operating Mode (Fig. 11).




Fig.11: Choosing OLS Router operating mode.

Then, at the same window. Go to OLSR Routing (Optimized Link State Routing) section →

New Interface option. Select eth1 in the drop down list and click on Add button.

Interface eth1 will be added. It corresponds to the wireless interface in the Linksys WRT54GL

router (Fig. 12). After that, just click save and then Apply Settings button at the end of the page.



Fig. 12: Adding the eth1 interface to the OLSR configuration.

2.2 CLIENT COMPUTERS CONFIGURATION

Now, setup the computers in order so they can successfully connect and communicate with the

routers.

First, we need to set a static IP on the same subnet as the routers.

Go to wireless interface → Properties (Figs. 13 - 15).

Insert the IP: 10.1.1.X. and subnet mask 255.255.255.0.

Where X could take values from 25 to 254. It will depend of the number of clients.

For your demo you could chose:

Client 1: 10.1.1.50

Client 2: 10.1.1.30



Fig. 13: Wireless Network Connection properties.

Fig.14: Select Internet Protocol (TCP/IP) and click on Properties.




Fig.15: Setting up a static IP.



2.3 DEMO

This will be the DEMO that you will have to implement the day of the evaluation. The next sections explain the procedure used to test the DEMO and verify that it’s working.

2.4 OLSR

Now, download and install olsrd-0.5.6, which is an implementation of the OLSR protocol. It

allows mesh routing for any network equipment and it is available for many operating systems.

Link: http://olsr.org/releases/0.5/olsrd-0.5.6-r3-pre-cac1df64dcd5-setup.exe

Once we have installed olsrd on windows. Its shortcut will be on the desktop (Fig. 16). It is

recommendable to restart the system before use it for the first time.

Fig.16: Olsrd shortcut.

http://olsr.org/releases/0.5/olsrd-0.5.6-r3-pre-cac1df64dcd5-setup.exe



After reboot the system, starts the olsrd program. Select the interface which has our IP address

and then click Start (Fig. 17).

Fig. 17: Setting up olsrd on the computer.



Next few tabs are just for information (Figs. 18-20).

Fig. 18: Logs.



Fig. 19: Nodes discovered by the OLSR protocol.



Fig. 20: Routes created by OLSR.

Congratulations!

At this point, we have finished setting up the routers and the laptops, with these configurations

we achieve a WMN with the OLSR routing protocol.

2.4 PERFORMANCE TESTS

After everything has been setup, it is possible to do some network analysis. First, use Wireshark

to see the OLSR packets are being sent out to the broadcast address of our subnet (10.1.1.255)

(Fig. 21).

Link: http://media-2.cacetech.com/wireshark/win32/wireshark-win32-1.2.13.exe

OLSR is working well. It is using the port 698. Furthermore, we can see the 2 routers and 3

clients connected to the mesh.




Fig. 21: Wireshark analyzing packets sent to the network.



Then, use tracert command to determine the number of hops needed to communicate with Router

1. In this case it achieved 2 hops (Fig. 22)

Fig. 22: Running tracert to see the hop numbers.

CONCLUSIONS

In this project we learn:

How to set up a Wireless Mesh Network with OLSR step by step.

We did some performance tests to see how works the WMN in a real testbed.

We observed some properties of WMNs, such as self-forming, self-healing, and self-

organizing.

o Because, when we disconnected a router, the client that was connected to it

automatically connects to another router.

How to install DD-WRT firmware into the Linksys WRT54GL Router.

APPENDIX A: SOFTWARE TO DOWNLOAD

DD-WRT v24-sp1

o Download these 2 file images

dd-wrt.v24_mini_generic.bin

dd-wrt.v24_std_generic.bin

o from: http://www.dd-wrt.com/dd-wrtv3/dd-wrt/downloads.html

Olsrd-0.5.6



o Download the version 0.5.6-r3-pre from Nov 2008

o from http://www.olsr.org/?q=download

Wireshark-win32-1.2

o Download Windows Installer (32-bit)

o from http://www.wireshark.org/download.html

REFERENCES

1. I.F. Akyildiz and Xudong Wang, “A survey on wireless mesh networks,” IEEE

Communications Magazine 43, no. 9 (2005): S23-S30.

2. T. Clausen and P. Jacquet, eds., “Optimized Link State Routing Protocol (OLSR),” 2003.

3. G.R. Hiertz et al., “Principles of IEEE 802.11s,” in Computer Communications and

Networks, 2007. ICCCN 2007. Proceedings of 16th International Conference on, 2007,

1002-1007.

4. Matthew Gast, 802.11 Wireless Networks: The Definitive Guide, Second Edition, 2nd ed.

(O'Reilly Media, Inc., 2005).

5. Ron Fuller and Tim Blankenship, Building a Cisco Wireless LAN, 1st ed. (Syngress,

2002).

6. Pejman Roshan and Jonathan Leary, 802.11 Wireless LAN Fundamentals (Cisco Press,

2004).

7. Johnathan Ishmael et al., “Deploying Rural Community Wireless Mesh Networks,” IEEE

Internet Computing 12, no. 4 (2008): 22-29.

WEBS

http://en.wikipedia.org/wiki/Linksys_WRT54G_series

http://www.dd-wrt.com

http://www.dd-wrt.com/wiki/index.php/Installation#Precautions

http://www.dd-wrt.com/wiki/index.php/WRT54G_v4_Installation_Tutorial

http://timbermheay.wordpress.com/2007/11/12/how-to-install-dd-wrt-on-linksys-wrt54gl-

wireless-router/

OLSR main page (http://olsr.org/?q=download)

http://www.e-bulles.be/bubble/Olsr.conf

http://www.google.com/url?q=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FLinksys_WRT54G_series&sa=D&sntz=1&usg=AFrqEzeP1Ob40UvCF_-9cFdkL3UDZveXjA

http://www.google.com/url?q=http%3A%2F%2Fwww.dd-wrt.com%2F&sa=D&sntz=1&usg=AFrqEzdpaAEl0azxjUGm55mbal57TjelNA

http://www.google.com/url?q=http%3A%2F%2Fwww.dd-wrt.com%2Fwiki%2Findex.php%2FInstallation&sa=D&sntz=1&usg=AFrqEzd3MavTseifSVFShpP7X2ltXRgsFg

http://www.google.com/url?q=http%3A%2F%2Fwww.dd-wrt.com%2Fwiki%2Findex.php%2FWRT54G_v4_Installation_Tutorial&sa=D&sntz=1&usg=AFrqEzd9qF_hx8ZW86U4tdJD2F6AtbEEBA

http://www.google.com/url?q=http%3A%2F%2Ftimbermheay.wordpress.com%2F2007%2F11%2F12%2Fhow-to-install-dd-wrt-on-linksys-wrt54gl-wireless-router%2F&sa=D&sntz=1&usg=AFrqEzdYUm2PmyMDW_L57HCu8p4JK8mPPg

http://www.google.com/url?q=http%3A%2F%2Ftimbermheay.wordpress.com%2F2007%2F11%2F12%2Fhow-to-install-dd-wrt-on-linksys-wrt54gl-wireless-router%2F&sa=D&sntz=1&usg=AFrqEzdYUm2PmyMDW_L57HCu8p4JK8mPPg

http://www.google.com/url?q=http%3A%2F%2Folsr.org%2F%3Fq%3Ddownload&sa=D&sntz=1&usg=AFrqEzcDo2d05dG_ZUFF3z02uERaNBNGjA

http://www.google.com/url?q=http%3A%2F%2Folsr.org%2F%3Fq%3Ddownload&sa=D&sntz=1&usg=AFrqEzcDo2d05dG_ZUFF3z02uERaNBNGjA

http://www.google.com/url?q=http%3A%2F%2Fwww.e-bulles.be%2Fbubble%2FOlsr.conf&sa=D&sntz=1&usg=AFrqEzdpvM4bqLbdgE-ygyQABeGncmqvPQ

Documents

Building a Wireless Mesh Network