My home network has two wireless access points operating on two frequencies. My main Airport Express which is operating on 802.11n in the 5 gigahertz spectrum and a Linksys WRT54G (dd-wrt) which is operating on 802.11g/b in 2.4 GHz land.
This allows me to have full-speed on my 'n' devices which can operate in the clear airspace of 5 Ghz while still allowing legacy devices on 2.4 Ghz. I wish I had the latest Airports which had dual tuners, allowing for both at the same time, but this is the cheap way to get the same effect.
Recently, I wanted to check on my WRT54G but forgot its static IP address. It's in bridge mode, which means that it's not serving IP addresses itself and is basically invisible to the network. Good for devices connecting through it, not good if you want to update its settings.
I was struggling with remembering its IP addresses and thought I'd have to basically try all the IPs (10.0.1.2.... ping 10.0.1.3... 10.0.1.4....) when I remembered a UNIX hack:
Karens-Neo-MacBoopPro:~ nakamura$ ping 10.0.1.255 PING 10.0.1.255 (10.0.1.255): 56 data bytes 64 bytes from 10.0.1.35: icmp_seq=0 ttl=64 time=0.069 ms 64 bytes from 10.0.1.1: icmp_seq=0 ttl=255 time=0.957 ms (DUP!) 64 bytes from 10.0.1.9: icmp_seq=0 ttl=255 time=1.409 ms (DUP!) 64 bytes from 10.0.1.201: icmp_seq=0 ttl=64 time=5.339 ms (DUP!)
I pinged the network broadcast address (10.0.1.255) and all the devices on the network responded. The only device in the list I didn't recognize was 10.0.1.201. that was my router!