ethernet - Networking - Shared to other Computers - How to find a client's IP address? - Ask Ubuntu

the hardware this:

• laptop internet access via wifi. router practically inaccessible.
• headless banana/raspberry/your-favorite-flavor pi needs sd image , additional packages.

so temporary crossover cable between pi , laptop, setup laptop's ethernet port "shared other computers" (*), image sd card, , boot pi. now, address pi have can ssh it?

i don't have force particular address, like question wants. want know is.

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(*) network notification -> edit connections... -> wired connection 1 -> edit button -> ipv4 settings tab -> method = shared other computers

there's couple things can do. assuming you've got single ethernet connection going laptop raspberry, arp-scan suffice. first , figure out what's name of ethernet interface. in case that's eth3. thus, here's example:

bash-4.3$ sudo arp-scan -i eth3 --localnet [sudo] password xieerqi:  interface: eth3, datalink type: en10mb (ethernet) starting arp-scan 1.8.1 256 hosts (http://www.nta-monitor.com/tools/arp-scan/) 10.42.0.40  b8:27:eb:96:38:91   (unknown)  1 packets received filter, 0 packets dropped kernel ending arp-scan 1.8.1: 256 hosts scanned in 1.459 seconds (175.46 hosts/sec). 1 responded 

in output can see raspberry has 10.42.0.40 ip address.

the arp-scan simple approach , doesn't require sweat. alternative methods can used too. here's few of them:

• knowing network's first 3 octets (for example via ip addr show eth3 command in case), write simple script pings range of hosts. ( see below python script ).
• fping alternative standard ping command, allow host range probed
• you can use nmap perform host discovery in variety of methods. in particular, command: nmap -e eth3 -sn 10.42.0.0/24 work best - instructs nmap perform host discovery -sn option ( underneath hood sends arp requests broadcast mac address), on interface specified -e option. 10.42.0.0/24 cidr notation network. quite simple.

• wireshark can used capture packets on ethernet interface. of course , raspberry has send out packets in first place them captured, might not work if don't have "talkative" raspberry. can , however, start capture, filter udp protocol, unplug , plug in raspberry. should see dhcp request , response going it

  

• devices build arp table on time when hosts appear/disappear network, use arp -a command.

• if you're using standard ubuntu , didn't install alternative dhcp servers, can check dnsmasq leases file ip assigned devices. instance:

  bash-4.3$ cat /var/lib/misc/dnsmasq.leases  1479095355 b8:27:eb:96:38:91 10.42.0.40 localhost * 

  see related question here:dhcp lease raspberry pi not found

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nmap , wireshark approaches quite useful if have ethernet switch several devices attached it.

since i've mentioned scripting ping, here's one:

from subprocess import * network = '10.42.0.' num in range(255):     = str(num)     dn = open('/dev/null','w')     try:         print('checking ' + network + i)         check_call(['ping', '-c','1', '-w',                     '1','-q',network + i],stdout=dn)     except calledprocesserror:         pass         #print('10.42.0.' + + ' down')     else:         print('>>> ' + network + + ' up') 

this ping range of 256 addresses of network ( 10.42.0.x ) , , indicate of hosts up. ping times out after 1 second, therefore take 256 seconds scan everything. if have 1 raspberry can edit script quit if ip responds ping, speeding process. create number of threads. arp-scan still remains faster alternative.