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5.3. Troubleshooting autodiscovery

Sometimes however autodiscovery does not function as you would like, for example a node might not see multicast traffic from other nodes. This has occurred with some PCMCIA ethernet drivers. One solution is to place the interface in promiscuous and or multicast mode as detailed below:

Aug 31 20:45:58 localhost kernel: openMosix configuration changed: This is openMosix #98 (of 1 configured)
Aug 31 20:45:58 localhost kernel: openMosix #98 is at IP address 10.0.0.98Aug 31 20:45:58 localhost omdiscd[1627]: Notified kernel to activate 
openMosix  Aug 31 20:45:58 localhost kernel: Received an unauthorized information request from 10.0.0.99
What you should to then is try to force your NIC into promiscuous and/ or multicast mode manually.
ifconfig ethx promisc
or
ifconfig ethx multicast 
You might also want to run
tcpdump -i eth0 ether multicast 
which will have the same effect but you will now also be able to see the packages yourself.

On some Layer 3 switches you other configs might be required. An openMosix user found out that on his Switch Summit48Si (Extreme Networks) he had to run

disable ipmcforwarding (to deactivate the routing of multicast paquets)
disable igmp snooping
before he was the different omdiscd's were able to see eachother, other switches might require similar configs.

Aug 31 22:14:43 inspon omdiscd[1422]: Simulated notification to activate openMosix
[root@inspon root]# showmap
My Node-Id: 0x0063

Base Node-Id Address          Count
------------ ---------------- -----
0x0063       10.0.0.99        1
[root@inspon root]# /etc/init.d/openmosix status
OpenMosix is currently disabled
[root@inspon root]# 
If you see the simulated you have probably forgotten to put the
#define ALPHA
in comment.

I have also noticed that autodiscovery does not work with FireWire based network cards.