I had following scenario:
client in client vlan
server multihomed in client vlan and server vlan with SLES 11.2 (I know that this is bad!)
the server didn’t respond to the ping from the client when the client pinged the srv vlan ip of this server. (ping came in on iface of the srv vlan but the server never send a reply)
I could proof this through tcpdump. After opening a service request at novell, the rp_filter was the solution. If this filter is set to one, the server won’t respond depending on the setting of this filter.
Set to 0 (deactivated) the server starts responding to the ping. For details please see:
# enable route verification on all interfaces
net.ipv4.conf.all.rp_filter = 1