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Many hosting providers put multiple ip addresses on same physical machine. If I have two ip address, for example: 192.168.1.100 and 192.168.1.101. If I can only send probing packets from afar, how can I tell if these ip addresses are hosted on same physical machine? Is there any tool I can use, such as nmap? Thanks!

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closed as off topic by EEAA, Shane Madden, ThatGraemeGuy, Iain Nov 22 '12 at 7:15

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Talk to the system administrator of that server. –  EEAA Nov 22 '12 at 6:52
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Does it respond to SSH or SSL? Does both IPs return the same certificate/public key when you attempt to connect? This would strongly indicate you are looking at a single host. Since it is a very bad idea to have the same private key on many systems. –  Zoredache Nov 22 '12 at 8:32

1 Answer 1

No - you're not terribly likely to be able to find this information unless you're on the same subnet as the IP addresses in question (in which case, ARP provides a fast and easy answer).

From outside the subnet, there are some tools you can use to potentially obtain more information. For instance, say SSH is listening on both addresses - do the services have different or the same public keys? Or, if you run an nmap OS detection scan, maybe the two addresses are detected as different operating systems? Maybe they're running BIND and you can query hostname.bind in the CHAOS class?

From a different network, you're depending on information gathering techniques that may or may not bear fruit. Don't count on it working.

(By the way, this assumes that we're talking about "same server" meaning the same logical node/OS stack. If we're talking about trying to find if two VMs are on the same physical server, forget about it - even on the subnet, you'd need access to the switches.)

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Fwiw if they are separate NICs as well as IP addresses ARP won't help you either. –  Mark Henderson Nov 22 '12 at 7:16
    
@MarkHenderson Ahh yeah, good point. –  Shane Madden Nov 22 '12 at 7:17

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