How to run more than two UST-10LX or UST-20LX in ROS using urg node?

edit

You will have to change the IP settings of one of your UST. After that use a router to connect Lidars with your PC. Then change IPV4 settings to manual and IP address to 192.168.0.100 (as told by hokuyo). After all this you will be able to run both the lidars individually using the command rosrun urg_node urg_node _ip_address:="192.168.0.10" for the lidar with default settings and _ip_address:="192.168.0.x" for new settings.

For launching both these together you can make a launch file. You can use:

<launch>
  <node ns="lidar1" pkg="urg_node" type="urg_node" name="lidar1" >
    <param name="ip_address" value="192.168.0.10"/>
  </node>
  <node ns="lidar2" pkg="urg_node" type="urg_node" name="lidar2" >
    <param name="ip_address" value="192.168.0.12"/>
  </node>
</launch>

It will work for sure. Cheers!