Can I monitor who is using my Mac OS X Internet Sharing?

Question

I'm running Snow Leopard and I'm sharing my Verizon connection via my Mac's built-in AirPort. Is there any way for me to identify who/what is using my shared connection?

System Preferences » Sharing » Internet Sharing: sharing my Internet access from my Verizon USB Modem (aka Pantech USB Modem) to other computers, through my AirPort card.

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I'm sharing my AirPort out to others as an Access Point.

(For Windows, see How can I find out who is using my Windows Internet Connection Sharing (ICS)?)

score 15 · Answer 1 · edited Jul 22 '21 at 05:45

I've figured out that the list of DHCP leases for the wifi that AirPort on the Mac publishes is kept in "/private/var/db/dhcpd_leases". This is not a list of currently connected clients, however. To figure out which "hosts" are still "up", I use the nmap utility (easily installed with Homebrew):

grep ip_address /private/var/db/dhcpd_leases | cut -d= -f2 | nmap -iL - -sn

Sample output:

...
Nmap scan report for 10.0.2.3
Host is up (0.74s latency).
Nmap scan report for 10.0.2.4
Host is up (0.11s latency).
Nmap done: 23 IP addresses (4 hosts up) scanned in 18.36 seconds

Next, lookup the same IPs back in the "dhcpd_leases" file to find out the client name and MAC address.

score 8 · Answer 2 · edited Aug 19 '11 at 10:37

8

If you want to graphically display all your local network connections, you may be interested in etherape. Otherwise, I'd go with @caliban

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edited Aug 19 '11 at 10:37

Gareth

19,080

answered Sep 29 '09 at 20:25

DaveParillo

14,761

score 6 · Accepted Answer · edited Aug 19 '11 at 10:37

Well, if your Airport is the only wireless router you have, you can always find out who is connected to it.

To do that :

Start Airport Utility
Double-click your Airport
Start Manual Setup mode
Navigate to Airport > Summary
Choose "Wireless Clients"

You should now see a complete list of the clients connected to your Airport.

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Alternatively, you might want to run a network sniffer program such as KisMAC or iStumbler.

EDIT : Question asked is actually referring to Internet Sharing using a Mac + in-build Airport as gateway.

In that case, since your Mac is the gateway + router, you can use a network mapper utility to "map" out the network, thus finding out who is connected. You can try NMap, an opensource network mapping utility.

score 4 · Answer 4 · answered Oct 13 '11 at 17:02

there is a way of listing dhcp addresses if you enter in terminal:

arp -i en1 -a

sample output (10.0.2.1) is your mac's default address as an airport router :

? (10.0.2.1) at 60:33:4b:20:2e:e2 on en1 ifscope permanent [ethernet]
? (10.0.2.2) at (incomplete) on en1 ifscope [ethernet]

score 2 · Answer 5 · answered Feb 18 '13 at 20:37

2

I like iftop, which you can install with MacPorts

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answered Feb 18 '13 at 20:37

John Douthat

691

score 2 · Answer 6 · edited Oct 08 '13 at 11:24

2

arp -i bridge0 -a

If you are using Internet Sharing on Mac OS X

edited Oct 08 '13 at 11:24

Sathyajith Bhat

62,374

answered Oct 08 '13 at 08:53

marjinn

31

Can I monitor who is using my Mac OS X Internet Sharing?

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