Using ' show ip DHCP bindings ' on a router operating as a DHCP server I have strange entries under the DHCP client-id/hardware address ( example below ) , should they correlate to the clients MAC address ?
IP address Client-ID/ Lease expiration Type
192.168.1.3 0063.6973.636f.2d30. Mar 16 1993 10:09 PM Automatic
192.168.1.4 0063.6973.636f.2d30. Mar 16 1993 10:10 PM Automatic
That string represents the ASCII equivalent of the client identifier. For eg. if you convert the client ID(0063.6973.636f.2d30.3030.612e.6238.3939.2e31.3163.352d.566c.3130.31) by using the ASCII table, you will get cisco-000a.b899.11c5-Vl101. The format cisco uses is cisco--. So here in your case I assume you assigned dhcp address to your vlan101 interface.
By default, DHCP implementations typically employ the client's MAC address for this purpose, but the DHCP protocol allows other options as well. In any case, in order for DHCP to function, you must be certain that no other client is using the client ID you choose, and you must be sure the DHCP server will accept it. What is termed the Client ID for the purposes of the DHCP protocol is whatever is used by the protocol to identify the client computer.
A client identifier (DHCP option 61) can be a hexadecimal or an ASCII value. By default, the client identifier is an ASCII value.That is what happens if you just use ip address dhcp without any options. You can override the default by using ip address dhcp client-id <interface> command, then it will use the hexadecimal MAC address of the named interface as the client identifier.
There is also DHCP option 12, that is used to send the hostname to the Server. By default option 12 also will be sent with the configured hostname as the value, but you can change it with ip address dhcp hostname host-name.