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Old 03-31-2016, 07:27 AM   #1
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NMAP always shows host down of my public IP

my pubic ip address always shows that host is down during scanning of open ports in nmap in kali linux BUT public ip in windows 7 shows up and shows the open ports.

can anyone help me how to resolve this problem in kali linux.?
Old 03-31-2016, 09:22 PM   #2
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This might be your issue perhaps...

Many firewalls and routers block or drop the ICMP (echo request, echo reply) ping. This is meant to obscure the presence of the hosts behind the firewall and protect against a possible DoS using the ping packet.

When you use nmap to scan a system or network, by default, it send out a ping to see if the host is up and if it gets a response, it then sends the specified packets to scan the system. If the ping is blocked or dropped, nmap gives up and says, "host is down."

To get around firewalls and routers that block or drop the ping, we need to suppress nmap's default behavior of sending out that initial ping and get past the firewall that is blocking us. We can do this by using the -P0 switch:

kali > nmap -sS -P0

In particular the 'Evading Firewalls' section.


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