[hpsdr] Hermes and Ethernet Switch Mystery

[John Marvin]

Joe, you haven't mentioned whether or not the switches you tried are at 
least 100 Mbit capable (if not they must be fairly old switches). If 
they are then the problem is most likely not the switch you are using, 
since you say that they are full duplex and appear to work properly as 
part of your computers connection to the internet.

my guess is that you have an issue with how Hermes gets its IP address. 
When directly connected both the PC and Hermes will use APIPA addresses 
in the 169.254.x.x range once their DHCP requests fail. When they aren't 
directly connected both the Hermes and your PC will send DHCP requests, 
where one may succeed and the other fail. If they both do not get 
responses then it should work the same as if they were directly 
connected (assuming your switch functions properly and is full duplex).

The question is where is the DHCP server on your network and how is it 
configured? If your PC gets a DHCP address and the Hermes does not then 
your PC will be on a "different" network than the Hermes, which will 
come up using an APIPA address. If you consult the Hermes User Manual 
page 16 documents the meaning of various LED's, and there is a group of 
10 leds together that contains "LED7" which indicates what the DHCP 
status for the board is. If the led is flashing rapidly this indicates 
that the DHCP request timed out and Hermes is using an APIPA address.

In most cases your DHCP server is going to be either a router or 
cable/DSL modem on your network (it will depend on whether or not a 
router is built into your "modem"). Since you've tried multiple 
switches, most likely the issue is your DHCP server configuration, 
although in most cases the default configuration should be adequate for 
almost any home network. Have you customized your DHCP configuration?

If you absolutely want to verify that the switch is not the problem then 
you should try just connecting your PC and your Hermes to the switch 
without connecting anything else to the switch (i.e. the rest of your 
home network where you DHCP server most likely resides). This would 
essentially be the same scenario as a direct connection, i.e. both your 
PC and Hermes will be using APIPA addresses. If this works then your 
switch is not the issue. If it doesn't then make sure that the switch is 
at least 100 Mbit capable and/or try yet another switch.

If you still can't find the problem it would be helpful if you share 
more about your network topology.

John
AC0ZG

On 12/10/2012 2:44 PM, Joe Giacobello, K2XX wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> If I plug my Hermes directly into the Ethernet port on my computer, PSDR
> connects with it without any problems. However, if I connect the Hermes
> and my computer to my Ethernet through a full duplex switch, PSDR cannot
> communicate with the Hermes although my computer can access the Internet
> and my home network. The LEDs on the line going to the Hermes shows a
> connection and activity, but apparently PSDR is not seeing the Hermes in
> this configuration. This has now occurred with two different full duplex
> switches. (BTW, when the Hermes is connected by a direct connection to
> the computer, it does not show up on the network devices window.)
>
> Anyone have any ideas what might be going on here?
>
> 73, Joe
> K2XX
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