[SOLVED] Finding the IP of a device

Question

Alright, so I installed arch on a computer and set sshd to run in the background. At the moment, the computer doesn't have a monitor, and the other computer in my room is a laptop (so no screen switching). I want to be able to log into the monitorless computer via ssh.
Anyway, both computers have a wired ethernet connection to a switch in my room (which is needed to get any connection at all by my university). They both get a dhcp-leased IP that is NOT on a subnet, meaning every device shows up as an independent IP when queried.
So, my question is this: is there a way I can figure out the IP of the monitorless server running ssh, so I can log into it? I know the hostname, if that helps.
Last edited by Ferrenrock (2010-02-10 13:09:23)

Answer 1

Sorry about the wait--I took mdickinson's advice and did a ping sweep with the cord unplugged. Originally, I had done it for all 255 addresses in the subnet and it had been impossible to figure out anything.
raf_king, fumbles: My wording was awful, partially due to the fact that half of what I said was wrong: what I meant to say was that every IP is a <b>public</b> IP (and not behind any sort of NAT), and while the switch in my dorm room might physically be a subnet of its own, address-wise the fourth octet corresponds to a subnet consisting of multiple rooms. Perhaps this will explain it:
[root@xaiwos ~]# ifconfig eth0 | grep inet
inet addr:130.126.66.100 Bcast:130.126.67.255 Mask:255.255.254.0
[root@xaiwos ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
130.126.66.0 0.0.0.0 255.255.254.0 U 202 0 0 eth0
0.0.0.0 130.126.66.1 0.0.0.0 UG 202 0 0 eth0
[root@xaiwos sampo]# nmap -sP 130.126.66.1-255
Starting Nmap 5.21 ( http://nmap.org ) at 2010-02-10 05:56 CST
Nmap scan report for uiuc-tri-net.gw.uiuc.edu (130.126.66.1)
Host is up (0.0017s latency).
MAC Address: 00:15:C7:24:7C:00 (Cisco Systems)
.......(blah blah blah 20 IPS)........
Nmap scan report for tri0752.urh.uiuc.edu (130.126.66.100) <--my laptop
Host is up.
Nmap scan report for tri0764.urh.uiuc.edu (130.126.66.112) <--my xbox
Host is up (0.00010s latency).
MAC Address: 00:22:48:77:74:AA (Microsoft)
.....(one hundred more IPs).....
But when I unplugged the switch from everything else, I got
[root@xaiwos sampo]# nmap -sP 130.126.66.1-255
Starting Nmap 5.21 ( http://nmap.org ) at 2010-02-10 06:25 CST
Nmap scan report for 130.126.66.100
Host is up.
Nmap scan report for 130.126.66.112
Host is up (0.00010s latency).
MAC Address: 00:22:48:77:74:AA (Microsoft)
Nmap scan report for 130.126.66.150
Host is up (0.00013s latency).
MAC Address: 00:E0:4C:39:9B:08 (Realtek Semiconductor)
Nmap done: 255 IP addresses (3 hosts up) scanned in 29.16 seconds
After that, the answer was pretty clear which one was the mystery computer.
And now I just remembered that I forgot to change the hosts.allow file on that other computer....crap....