06-25-2017 12:41 PM - edited 03-03-2019 08:35 AM
Hi I have a strange situation with my DHCP pool.
As you can see below, I made some reservation for the first 3 devices.
The thing I do not understand is that the devices get another IP address? Moreover, their Mac address is transfomed:
From 008e.7135.b000 to 0100.7135.4db0.00
From 008e.7135.b440 to 0100.7135.4db4.40
From b835.4789.8465 to 01b8.3547.8984.65
Why? Where does it come from?
Thanks!
<code>sh ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
192.168.100.1 0071.354d.b000 Infinite Manual
192.168.100.2 0071.354d.b440 Infinite Manual
192.168.100.3 b835.4789.8465 Infinite Manual
192.168.100.6 0100.7135.4db0.00 Jun 26 2017 02:08 PM Automatic
192.168.100.7 0100.7135.4db4.40 Jun 26 2017 02:59 PM Automatic
192.168.100.8 01b8.3547.8984.65 Jun 26 2017 04:55 PM Automatic
sh mac
Destination Address Address Type VLAN Destination Port
------------------- ------------ ---- -----------------
7648.7a42.ffc6 Self 1 Vlan1
0071.354d.b000 Dynamic 1 GigabitEthernet0
b835.4789.8465 Dynamic 1 GigabitEthernet0
0071.354d.b440 Dynamic 1 GigabitEthernet0
</code>
06-25-2017 03:59 PM
008e.7135.b000 sounds like a MAC address. 0100.7135.4db0.00 sounds like a DHCP client identifier.
You can match on either in your DHCP pool.
06-26-2017 12:09 AM
Thanks for the answer.
Why does the devices get another IP address?
06-27-2017 04:58 AM
Hi,
this document may answer your questions:
Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks
Setting Manual Bindings
There are two ways to set up manual bindings; one is for the Windows host, and the other is for non-Windows hosts. There are two different commands used to configure; one is for Microsoft DHCP clients, and the other is for non-Microsoft DHCP clients: DHCP client-identifier (manual binding - Microsoft DHCP clients) and DHCP hardware-address (manual binding - non-Microsoft DHCP clients). The reason for two different commands is that a PC that runs with Windows modifies its MACs, and a 01 is added at the beginning of the address. These are the sample configurations:
•The following is the configuration for Microsoft DHCP clients
configuration terminal
ip dhcp pool new_pool
host ip_address subnet_mask
client-identifier 01XXXXXXXXXXXX
!--- xxxxxx represents 48 bit MAC address prepended with 01
•The following is the configuration for non-Microsoft DHCP clientsconfiguration terminal
ip dhcp pool new_pool
host ip_address subnet_mask
hardware-address XXXXXXXXXXXX
!--- xxxxxx represents 48 bit MAC address
I think the distinction between MS and non-MS clients in the document is a bit oversimplified; the actual question is whether or not the clients use DHCP option 61 (see RFC 2131 4.2 and RFC 2132 9.14). If so, you need to prepend a '01' as shown in the first configuration example.
HTH
Rolf
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