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earlier this week we physically installed a machine in our server rack and connected it to our network switch. It has Scientific linux installed but we don't have a user account set up to log into. We turned it on and its running headless, but we'd like to verify that it is able to communicate on our internal network/connect to the internet through our network, because remotely right now we can't even verify that its on. Is there something we can run from another machine on our network to find it (we have its mac address) or list all machines on our local network? thanks

we've tried solutions on this server fault thread using nmap, ip neigh, and arp to scan through our local ip range and then grep for our mac address but got nothing

nmap -sP <our IP range> | grep -i "<the machine's mac address">
sudo arp -a | grep -i "<the machine's mac address">
sudo ip neigh | grep -i "<the machine's mac address">
James Yoe
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  • Please check [https://stackoverflow.com/questions/11966776/check-host-availability-by-mac-address] – J.M. Robles Nov 03 '17 at 20:52
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    Have you ever checked if the server actually boots, if you can actually get login prompt or ping before or is this your first attempt to connect? – EvilTorbalan Nov 03 '17 at 21:16
  • If the server has the wrong ip you cannot mmap it this way. You should see the Mac in the Mac table of the switch. If you think basic setup should work, then you can also run tcpdump on broadcast packets and then restart the machine. – eckes Nov 04 '17 at 17:01

2 Answers2

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Hows your server connected to your network via router,firewall etc If you are using managed switches then you can check in the console or if your using a firewall/router then you can check its mac address and try to get its ip address

Also you can check if you were running any services like apache etc on your server then you can port scan or manually check by Telnet if you had opened ports for your local subnet

Physically check the Ethernet cable and trace it to port of switch or router and try to get its ip

Last one you can try using wireshark to trace communication and track your server,how to use wireshark

Vijay Muddu
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It sounds like you think your headless host may be a DHCP client, and you want to verify that it obtained an IP.

To toggle connectivity, go visit your host. Note the green ethernet LED showing good link status, on both ends of the CAT-5 cable. Momentarily unplug and notice that both link lights go out. Plug back in, producing a "link up" event that will trigger a new DHCP client request.

On your DHCP server, tail -f the log, or look at current leases and lifetimes both before and after toggling connectivity. Once you have an IP, ping it continuously and note the absence of replies for the few seconds that the host's ether is manually disconnected. Concurrently running tcpdump -e port bootpc or arp may prove helpful.

If that's not feasible, use fping (or nmap) to scan your local IP prefix, and note the one IP that is present or absent according to whether the host's ether is manually disconnected. You reported that you have already scanned your subnet from a server on that subnet, without seeing the desired MAC address appear in the server's ARP table, so it's likely your headless server is powered off or at least not part of that IP subnet.

J_H
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