I'm trying to determine a server IP address via ping and open ports/services by running an NMAP scan.

At work, when I ping my website/server, I get a response from 172.16.XX.X.

If I run an NMAP scan, it brings a back a list of open ports/services. As expected.

However, from my home computer, when a ping is sent, I get a response from a completely different address 69.XXX.XXX.XX

If I run an NMAP scan on this address, it only brings back primary and secondary mail servers. mail.xxx.ca and mail2.xxx.ca.

Some things to note:

At work (scenario one), I am behind a firewall.

I know there is an FTP service running on this server/website.

This site requires HTTPS, and HTTP request are redirected to HTTPS.

Does anyone know why these would be so different?

  • 1
    The second octet of the 172.x.x.x address would be helpful. Sounds like it might be an internal address (172.[16-31].x.x) which could be the firewall or some network security device/proxy at your work network. – armani Apr 6 '15 at 17:32
  • @armani see edit – Mark Apr 6 '15 at 17:38
  • Please review material regarding private and public IP blocks. Private IP blocks cannot be routed over the Internet and are NAT'ed. – schroeder Apr 6 '15 at 18:01

172.16.x.x is a reserved LAN IP, meaning your workplace has likely a proxy for traffic outbound to the Internet that must be intercepting your nmap scan. This is why you are getting a different IP and different results when scanning from work versus scanning from home.

  • Not necessarily a proxy, but simply NAT. – schroeder Apr 6 '15 at 18:01

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