how to find DHCP client list for Mac OS x 10.9.2

Do not use Airport Utility 5.6.

Here is a much more current version:

http://support.apple.com/kb/DL1664

I'm glad you have AirPort Utility 6.3.2, as that is the current version. I could not find a link to send you for 6.3.2. That is why I sent the 6.3.1 link, thinking the Utility would tell you that it needed an update.

I assumed from your initial post you were trying to run some very old AIrPort Utility, since you mentioned 5.6.

Under AirPort Utility 6.3.2, I found this help:

Reserve a DHCP address for client computers

Set up your base station or your AirPort Time Capsule to reserve a DHCP address for each client computer on your network. When a client computer joins your network, your base station or AirPort Time Capsule provides the same DHCP address to that client.

Your base station or AirPort Time Capsule must be set up to provide IP addresses to client computers on your network using DHCP before you can make a DHCP reservation.

1. Open AirPort Utility, located in the Utilities folder in the Applications folder.
2. Select the device you want to set up, then click Edit. Enter the password if necessary.
3. Click Network, and then choose either DHCP and NAT or DHCP Only, from the Router Mode pop-up menu depending on how you want to use DHCP.
4. Click Add ➕ below the DHCP Reservations list.
5. Choose DHCP Client ID or MAC Address from the Reserve by pop-up menu, depending on how you want to identify the client for the reservation. Then enter the Client ID or the MAC address.
6. Enter the IPv4 address you want to reserve for the client from the range of IP addresses your wireless device distributes.

Download the fing app on an iOS device, shows both clients

Still doesn't answer the question. Features have been stripped from AU from some time ago. Not good.

I'm using LanScan. It's OK.

Cheers