Thomson TG787v and PXE boot

If you have a Thomson TG787v modem, like we have from KPN Business in the Netherlands, you might want to add an PXE server to your network to quickly install computers without the hassle of running around with CDs or thumb drives.

I will not explain how to set up the PXE environment itself (which is in fact a TFTP service) but I will stick to the modification of the modem/router. This modification can NOT be done using the webbased configuration panel.

We will log in using telnet, create option templates for the DHCP server, install those option templates and finally add them to the active pool so they will actually be in use.

If you think that’s rather a lot of work to install option 66 (TFTP server address) and option 67 (Bootfile name) into your modem, please complain to Thomson and insist they make it a) more intuitive; b) improve their documentation; c) implement these things in their web-based configuration; d) all of the above.

  • Log in on the CLI using telnet at your router, port 23 and enter your credentials
    Note: with the unlocked versions, your login will be the username from the web-based configuration and no password. Try “Administrator”.
  • Install the new template for the PXE server address:
    dhcp server option tmpladd name=tftp_server_name optionid=66
  • Install the new template for the PXE bootfile name:
    dhcp server option tmpladd name=bootfile optionid=67
  • Instantiate the templates:
    dhcp server option instadd name=tftp_server_name tmplname=tftp_server_name value=(addr)
    dhcp server option instadd name=bootfile tmplname=bootfile value=(ascii)pxelinux.0

    Note: The file name can be configured to whatever you need.

  • List all DHCP server pools: dhcp server pool list
  • Optionally, add the option to the desired pool:

    dhcp server pool optadd name=LAN_private instname=tftp_server_name
    dhcp server pool optadd name=LAN_private instname=bootfile

It seems that the template instantiation is added by default to the “LAN_private” pool.

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