다음과 같은 명령어를 쓰면 됩니다.

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# echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all
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/etc/rc.d/rc.local 의 마지막에
추가하면 부팅시에 자동으로 적용됩니다.

[예]

[root@www logs]# ping phpschool.com
PING phpschool.com (210.108.91.167) from 210.108.91.167 : 56(84) bytes of data.
64 bytes from 210.108.91.167: icmp_seq=0 ttl=255 time=0.1 ms
64 bytes from 210.108.91.167: icmp_seq=1 ttl=255 time=0.1 ms
64 bytes from 210.108.91.167: icmp_seq=2 ttl=255 time=0.0 ms

--- phpschool.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.0/0.0/0.1 ms


[root@www logs]# echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all


[root@www logs]# ping phpschool.com
PING phpschool.com (210.108.91.167) from 210.108.91.167 : 56(84) bytes of data.

--- phpschool.com ping statistics ---
14 packets transmitted, 0 packets received, 100% packet loss
[root@www logs]#