[RndTbl] auto-IP

Robert Keizer robert at cluenet.org
Thu Nov 19 19:49:51 CST 2009

Dan Martin wrote:
> I am wondering how I can connect my Mac to a device over ethernet, 
> when I have no control over the device's IP address.
> I recently purchased HDHomeRun, a dual TV tuner that connects via 
> ethernet.  The idea of it is to be able to stream video content to any 
> machine on your network.
> My network has static IP addresses, so just plugging it into the hub 
> and searching for the device does not work.  I understand that it is a 
> DHCP client.  There is no documentation with the device, such as a 
> default IP address if one exists.
> I will only use the video on one machine at present, my Mac. 
>  Wikipedia indicates that the device "will also work via an auto IP 
> <http://en.wikipedia.org/wiki/Link-local_address> address if no DHCP 
> server is available".  Instructions meant for Windows (different 
> document) talk about assigning an IP address of 169.254.x.x to the 
> network interface.
> I am far from clear on how that works.  If the NIC I use to attach the 
> HDHomeRun has such an IP address, does the HDHomeRun know to configure 
> itself with a similar address?  The Mac's network preferences GUI 
> allows 4 choices:  DHCP, DHCP with manual address, BootP, and Manual. 
>  None of these seems to work.
> I can't even be sure if the device works - but LEDs come on.
> Does anyone have suggestions, other than changing my entire network to 
> DHCP?  Can you have some nodes on a network get addresses by DHCP 
> while others are static?
> -Dan
> Dan Martin
> GP Hospital Practitioner
> Computer Scientist
> ummar143 at shaw.ca <mailto:ummar143 at shaw.ca>
> (204) 831-1746
> answering machine always on
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The simplest solution to solve your problem in my opinion would be to 
setup a dhcp server. If you're not positive that the device actually 
uses dhcp by default you could plug it into your laptop, turn it off, 
start wireshark or another packet monitor and see if it broadcasts.

With a dhcp server you can specify specific IP addresses for specific 
mac addresses, meaning that you wouldn't have a problem with running 
static IP's only, since it would be possible to continue your current 
numbering pattern without problems.

Limiting the dhcp server to only give an address to a specific mac 
address would be the way I would go, once you've made sure that the 
device actually broadcasts looking for an address.

All the best,
Robert Keizer

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