[LINUX][RHEL6] 리눅스 서버에 ICMP Ping 패킷 차단하기
1. ICMP Ping 응답확인
Ping 명령을 통해 패킷 4개만 전송해보자
[root@rhel6-test ~]# ping -c 4 localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.013 ms
64 bytes from localhost (127.0.0.1): icmp_seq=2 ttl=64 time=0.026 ms
64 bytes from localhost (127.0.0.1): icmp_seq=3 ttl=64 time=0.025 ms
64 bytes from localhost (127.0.0.1): icmp_seq=4 ttl=64 time=0.025 ms
--- localhost ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 0.013/0.022/0.026/0.006 ms
2. 차단적용
# sysctl -w net.ipv4.icmp_echo_ignore_all=1
net.ipv4.icmp_echo_ignore_all = 1
3. 현재적용 값 확인
# sysctl net.ipv4.icmp_echo_ignore_all
net.ipv4.icmp_echo_ignore_all=1
4. 다시 ICMP Ping 응답확인
[root@rhel6-test ~]# ping -c 4 localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
--- localhost ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 13000ms
-- 응답이 없음 확인
5. 리부팅시에도 적용
[root@rhel6-test ~]# vi /etc/sysctl.conf
net.ipv4.icmp_echo_ignore_all=1
6. 파라미터 적용확인
[root@rhel6-test ~]# sysctl -a | grep net.ipv4.icmp_echo_ignore_all
net.ipv4.icmp_echo_ignore_all = 1