Q:

How to find the IP address of an access point that I'm connected to?

I'm connected to an open network, I can see the BSSID and the SSID but I don't think DHCP is enabled because I don't get any IP.
so is there a way to find out what is it's IP remotely ?
and thanks 

A:

(Assuming Linux system)
Once you have the MAC address of the AP, e.g. via iwconfig:
$ iwconfig eth1

eth1     IEEE 802.11g  ESSID:"OSU_PUB"  
         Mode:Managed  Frequency:2.427 GHz  Access Point: 00:0D:9D:C6:38:2D
         Bit Rate=48 Mb/s   Tx-Power=20 dBm   Sensitivity=8/0  
         Retry limit:7   RTS thr:off   Fragment thr:off
         Power Management:off
         Link Quality=91/100  Signal level=-39 dBm  Noise level=-87 dBm
         Rx invalid nwid:0  Rx invalid crypt:860  Rx invalid frag:0
         Tx excessive retries:0  Invalid misc:39   Missed beacon:8

The AP has hw addr 00:0D:9D:C6:38:2D so you can use tcpdump to sniff for traffic from that hardware address, which usually will reveal the IP address of it as the source sooner or later:
$ tcpdump -i eth1 -s 0 -v -n ether host 00:0D:9D:C6:38:2D

tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
13:15:49.106475 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 (00:0D:9D:C6:38:2D) tell 192.168.1.2, length 28

If the AP responds to broadcast pings you could probably send a broadcast ping to its specific MAC address to elicit a reply, but there doesn't seem to be a tool capable of doing that.

