[LON-CAPA-admin] Fixed IPs address?

Raeburn, Stuart raeburn at msu.edu
Wed May 13 17:38:42 EDT 2020

Hello hk,

The main impact of a change to an IP address for a LON-CAPA node will be a temporary loss of full connectivity to other LON-CAPA nodes in the network.  A loss of connectivity to a particular remote node will persist until either (a) a restart of loncontrol on the remote LON-CAPA server/VM or (b) /home/httpd/perl/loncron is run on the remote server/VM.  

Note: if an institution has campus firewall rules for its LON-CAPA servers/VMs, in addition to the OS-level rules managed by LON-CAPA itself, then the loss of connectivity for your nodes will also persist until those rules include the new IP addresses.

The standard LON-CAPA cron file: /etc/cron.d/loncapa includes an entry to run /home/httpd/perl/loncron (as user www) at 5:10 am local time.  

A user with the domain coordinator role selected can also run loncron from the web GUI via:
Main Menu > Status of domain servers > "Update Connections and Refresh Status Information"

When loncron is run: (a) an up to date list of hostnames of LON-CAPA servers/VMs in the network will be retrieved from one of the Academic Consortium servers at MSU, UIUC and SFU; (b) OS firewall rules for access to the LON-CAPA port (5663) will be updated to allow access from the IP addresses which the DNS service used by the server/VM maps for the current hostnames of LON-CAPA nodes in the network; (c) a USR2 signal will be sent to the lond parent process, which will (i) kill any lond child processes for which the client IP address no longer matches any of those in the network; and (ii) reload the Apache web server.

In the case where an institution has set-up firewall rules for the campus border which restrict inbound traffic to port 5663 on the institution's LON-CAPA servers/VMs, the team which manages the campus firewall will also need to update the rules to allow connections from the new IP addresses.

On way to avoid the need to change IP addresses would be to ask your network team to establish a VLAN which encompasses both the current building and the other building.  That way you could continue using the same IP addresses during the upcoming power outage when your hardware is moved, and there would be also be longer term benefits in terms of disaster recovery preparedness.

Stuart Raeburn
LON-CAPA Academic Consortium
From: LON-CAPA-admin <lon-capa-admin-bounces at mail.lon-capa.org> on behalf of H. K. Ng <hkng at fsu.edu>
Sent: Wednesday, May 13, 2020 4:10 PM
To: list about administration and system updating
Subject: [LON-CAPA-admin] Fixed IPs address?

Hi all,

Do the loncapa servers IP addresses have to be fixed? Unfortunately, there is a planned power outage in our building for 3 days!! and my thought is to move the servers to another building but it is on a different subnet. What are the ramifications for doing this?


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