With Oracle Linux kernel 2.6.31, which also includes Oracle Unbreakable Enterprise Kernel 2.6.32, a bug has been fixed in the Reverse Path Filtering. As a consequence of this correction, Oracle RAC systems that use multiple NICs for the private interconnect now require specific settings for the rp_filter parameter. This requirement also applies to all Exadata systems that are running Linux kernel 2.6.32 and above. Without these rp_filter parameter settings systems, interconnect packets can be blocked or discarded.

The rp_filter values set the Reverse Path filter to no filtering (0), to strict filtering (1), or to loose filtering (2). Set the rp_filter value for the private interconnects to either 0 or 2. Setting the private interconnect NIC to 1 can cause connection issues on the private interconnect. It is not considered unsafe to disable or relax this filtering, because the private interconnect should be on a private and isolated network.

For example, where eth1 and eth2 are the private interconnect NICs, and eth0 is the public network NIC, set the rp_filter of the private address to 2 (loose filtering), the public address to 1 (strict filtering), using the following entries in /etc/sysctl.conf:

net.ipv4.conf.eth2.rp_filter = 2
net.ipv4.conf.eth1.rp_filter = 2
net.ipv4.conf.eth0.rp_filter = 1