Ping -c1, wait for all responses from broadcast

networkingping

I want to send one packet to the broadcast address, but wait for all responses.

If I do ping -c 1 192.168.1.255, it sends just one packet, but it quits after getting the first response.

Best Answer

How would ping know that the responses it got really are all of them?

To find out which hosts on a subnet are up, something like nmap is well suited. See the -sn argument for Host Discovery:

-sn (No port scan)

This option tells Nmap not to do a port scan after host discovery, and only print out the available hosts that responded to the scan. This is often known as a “ping scan”,[...]

Systems administrators often find this option valuable as well. It can easily be used to count available machines on a network or monitor server availability. This is often called a ping sweep, and is more reliable than pinging the broadcast address because many hosts do not reply to broadcast queries.

Edit `/etc/sysctl.conf`

Add the following line to your /etc/sysctl.conf:

net.ipv4.icmp_echo_ignore_all=1

Then:

sysctl -p

Using iptables:

iptables -I INPUT -p icmp --icmp-type echo-request -j DROP

With cron

Run crontab -e as root, then add the following line:

@reboot echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all

Start and enable the service:

systemctl start cron.service
systemctl enable cron.service

linux – Utility for Performing ICMP Testing (“Ping”) in One Direction

tcpdump can do this, and is available pretty much everywhere:

tcpdump -n -i enp0s25 icmp

will dump all incoming and outgoing ICMP packets on enp0s25.

To see only ICMP echo requests:

tcpdump -n -i enp0s25 "icmp[0] == 8"

(-n avoids DNS lookups, which can delay packet reporting and introduce unwanted traffic of their own.)

This allows you to find if it is receiving the packets from the other machine (from which you would e.g. ping it), so the problem is with the return path, or if they directly don't arrive.

Best Answer

Related Solutions

Linux – How to Disable Ping Response (ICMP Echo) Permanently

Edit /etc/sysctl.conf

Using iptables:

With cron

linux – Utility for Performing ICMP Testing (“Ping”) in One Direction

Related Question

Edit `/etc/sysctl.conf`