Host discovery with ICMP
1 Try to send some ICMP packets (AND) 2 Ping sweep
The easiest and fastest way to discover if a host is up or not is by trying to send some ICMP packets.
Send an echo request using a simple
If pinging a single host works, try a ping-sweep: Send out ICMP echo requests to every system on a particular network or subset of a network to determine which hosts are up.
ICMP error messages can be used to mask the source of a Distributed Denial of Service attack, and with such attacks being common, ICMP error rate limiting is often applied. To avoid filters to common ICMP echo request-response, use
nmapto send other types of ICMP packets. If scans still take incredibly long, try discovering hosts with a SYN scan or UDP scan instead.
Send a single echo request
# ping -c 1 192.168.122.10
Send echo requests to ranges:
# fping -g 192.168.122.0/24
Using nmap, send echo, timestamp requests and subnet mask requests:
# nmap -PEPM -sP -n 192.168.122.0/24