SLES 11 SP1 networking problems

SLES 11 SP 1 has inconsistent / unpredictable network behavior, dropped pings or nonfunctional NICs. 

Behavior may be noticed after fresh install of SLES 11 SP1, after an update to SLES 11 SP1, or 10 SP4.

SLES 11 (prior to update 1) did not properly enforce reverse path filtering. 
After updating to to SP 1, this has been fixed. 
As a result, it may appear that update one breaks the servers network in situations where the customer has asymmetric routing, as packets that come from an unexpected network (when the source/destination IP addresses of the packet are compared) are dropped. 
In this situation, the customer can work around this issue by changing a setting in /etc/sysctl.conf

Change:
net.ipv4.conf.all.rp_filter=1
to
net.ipv4.conf.all.rp_filter=2

This changes reverse path filtering from enabled/strict to enabled/loose.
To enable changes immediately without having to reboot, run 'sysctl -p'.
More details can be found here: www.novell.com/support/kb/doc.php?id=7007649

Edit:  Modifying net.ipv4.conf.all.rp_filter has been directly observed to have no effect specifically in SP2 - as well as confirmed here: http://www.softpanorama.org/Net/Internet_layer/Routing/martian_source.shtml 
Currently there is no work around other than to resolve whatever network issue is causing the problem.