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[LDM #DOZ-458327]: LDM connections to a downstream LDM client with a changing IP address (i.e. NAT )

Gregg,

Hello fellow Nebraska graduate . . .

Your question is more complicated than you might expect, as some of the
issues in following a moving hostname is at the Linux kernel level with the
ARP table.

Using the case where you have an LDM (spc.noaa.gov) that is feeding from
another LDM with hostname xyz.noaa.gov, and that hostname gets moved to a
new machine that has a different IP, at the very least, you would need to
restart the LDM on spc.noaa.gov, but that may not be enough. The
spc.noaa.gov kernel will be holding an ARP table entry from the original
MAC from xyz.noaa.gov, and it will generally only reload that ARP table on
the following conditions:

- reboot of spc.noaa.gov
- clear the ARP table on spc.noaa.gov, then restart LDM
- wait until the scheduled time for the kernel on spc.noaa.gov to refresh
the ARP table, and then restart LDM
- send an unsolicited ARP update from the new server of xyz.noaa.gov to
spc.noaa.gov, then restart LDM

The LDM will get its host information from the OS, so the thrust of the
restart will also need to insure the OS is understanding that there was an
IP change.

Let me know if that does not answer your question or explain what would be
needed.
-
Stonie Cooper, PhD
Software Engineer III
NSF Unidata Program Center
University Corporation for Atmospheric Research
I acknowledge that the land I live and work on is the traditional territory of 
The Pawnee, The Omaha, and The Otoe.

Ticket Details
===================
Ticket ID: DOZ-458327
Department: Support LDM
Priority: Critical
Status: Open
===================
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