I discovered a wonderful utility last night: nast. I wanted to scan my local network, just to see what devices were on it, what their addresses were, etc. I could ping my entire subnet, but what if I had a machine that rejected ICMP packets? (Not that I do very often, but it can happen in larger environments). I thought using a protocol like ARP would be much more robust, since it is pretty much guaranteed to be available. Then I discovered nast.
nast can do a lot of neat things. The first I found was mapping a subnet of course, which you can do by running
1 | sudo nast -i eth1 -m |
This returns something like:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | Nast V. 0.2.0 Mapping the Lan for 255.255.255.0 subnet ... please wait MAC address Ip address (hostname) =========================================================== 00:1A:4D:9C:6D:30 192.168.1.5 (B74kB0x.home) (*) 00:18:01:2E:5F:66 192.168.1.1 (Wireless_Broadband_Router.home) 00:04:4B:03:2F:0D 192.168.1.2 (MediaServer.home) 00:21:5A:35:E0:43 192.168.1.3 (new-host.home) (*) This is localhost Finished |
nast can also try to find out if there are any nodes on your subnet acting in promiscuous mode, which I think is pretty hot. Check out the main nast page for the full feature set.
In my searching, I also came across fping. Its main improvements over regular old ping are:
- More than one host can be passed (as well as a file containing hosts)
- Output is very simple and easy to parse, making it ideal for scripting
- Tries each host and moves on if there is no response, making the whole process faster
Instead of
1 | ping -c 1 myhost1 ; ping -c 1 myhost2 |
you can just run
1 | fping myhost1 myhost2 |
which just returns
1 | myhost1 is alivemyhost2 is alive |
Both nast and fping are available in the Ubuntu repos.
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