I have a customer there had some UDP packets loose. I found this 4 following triggers:
Â SLES 11 with SP2.
Â Alias IP configured on an interface.
Â IP traffic send as UDP without any checksum in the header to the alias IP address.
Â No route to the source IP address.
If all 4 triggers where true, the IP packet will be drop by the kernel.
I could reproduced it with netcat.
The fix where to make a route to the source IP address.
Does anyone have any explantion on this behavior ?
SLES 10 SP2 donÂ´t behavior like SLES 11 SP2. SLES 10 SP just forward the packets as expected.
I assume this is a custom application sending these packets and you’re seeing some counter increase - or do you monitor the network?
Did I grasp that right that the application is sending out packets to a destination IP address that is configured as a secondary IP address on the (only) network interface of the sending host?
As you’re explicitly mentioning “without any checksum in the header” - is that checksum “0”? AFAICT a checksum field has to be present
Is offloading configured for the physical adapter?
Any messages in “dmesg” or syslog?
“no route to the source address” sounds strange - if the above is correct, the source address ought to be one of the local interface IP addresses - and you ought to have a routing table entry for that network.
Could you please give some more details, probably enriched by the output of “ifconfig”, “netstat -rn” etc?