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To make that permanent, you need to add the below line in /etc/nf fileĭoing a TCPDUMP on the machine, with icmp disabled will show you only echo_requests, because all ICMP request are ignored by the machine(No reply of any kind, so there is no mechnism to know whether its dropped or not). ~]# echo 1 ~]#Īn important thing to note in the above method is that, its only temporary.(In fact anything you modify on inside /proc will only stay until the reboot.) You can disable all ICMP traffic on a linux machine, by the following method. Related: How does TCP Three way Handshake work How to disable PING on Linux? Lets use two machine's to test this by disabling PING on them. A connection refused error with a RST package.A TCP connection to, well known publicly available ports like http,ftp,ssh etc.
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So below two methods can be used to determine whether the host is online or not, whenever PING is disabled or blocked. Even this information is more than enough to confirm the presence of the host. Whenever you try to establish a TCP connection to the remote host, the remote host will either accept the connection or refuse the connection by sending a RST package. In this kind of a situation, what you can do to check the host's presence is to telnet to a known port or to try making a TCP connection to the host. Due to which you cant ping the host, to check its presence. There can be instances where a remote host, has blocked ICMP traffic towards it.
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