eth0 or ppp0) are associated to a physical device. The easiest way is to create a virtual network interface. Your router can only be flashed from the IP 192.168.2.100. Create a virtual Network Interface on your Linux Box Using Suse Linux you can do this by yast or typing as root user: Trivial File Transfer Protocol (TFTP) is a very simple Filetransferprotocol.
Preparation Install the tftp package on your Linux Box
For flashing the Siemens Gigaset SE505, you have to use the dd-wrt.v23_mini_generic.bin.
This describes how to flash your Siemens SE505 Router using tftp and Suse Linux. Remember to follow the peacock thread first for background, use this page to identify your router model correctly, and use the dd-wrt download search page ( DD-WRT Downloads page or secure version) to ensure that you are getting the correct file (or files, as often is required) for the job. Please see Installation for more information. It is extremely important to follow the guidelines for your specific router.