http://z-issue.com/wp/linux-rhel-6-centos-6-two-nics-in-the-same-subnet-but-secondary-doesnt-ping/
# cat /etc/redhat-release
CentOS release 6.7 (Final)
# vim /etc/sysctl.conf
net.ipv4.conf.default.rp_filter = 2
net.ipv4.conf.all.rp_filter = 2
# sysctl -p
※ RHEL 6 이상부터의 변경된 사항
0 – No source validation
1 – Strict Reverse Path validation (RFC3704) – Packets are checked against the FIB (Forwarding Information Base), and only the best ones succeed
2 – Loose Reverse Path validation (RFC3704) – Packets are checked against the FIB, but only non-reachable BY ANY INTERFACE will fail
