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DHCP Port based address alloocation Subscriber-Id

I am trying to use the port based address allocation on my cisco 2960 catalyst switch. So the way it works is we force the dhcp server to use a subscriber id instead of client-id. You then tell it to create this subscriber-id from the interface-name. Now you reserve an ip address for a particular subscriber id so when a device is connected to a port it always receives the same Ip-address since it was assigned based on the subscriber id and not the client id.

Now in the step when you ask it to create the subscriber-id from the interface name, it is automatically generated based on the short name of the interface.

This works fine for interfaces such as: (they all start with 00 for some reason) Ethernet0/1 : Et0/1 : 0045 7430 2f31 FastEthernet0/1 : Fa0/1 : 0046 6130 2f31 GigabitEthernet1/0/1 : Gi1/0/1 : 0047 6931 2f30 2f31

Now here's what happens in my dhcp config:

Pool otgpool :
 Utilization mark (high/low)    : 100 / 0
 Subnet size (first/next)       : 0 / 0
 Total addresses                : 254
 Leased addresses               : 0
 Excluded addresses             : 1
 Pending event                  : none
 1 subnet is currently in the pool :
 Current index        IP address range                    Leased/Excluded/Total
 192.168.100.2        192.168.100.1    - 192.168.100.254   0     / 1     / 254
 1 reserved address is currently in the pool :
 Address          Client
 192.168.100.5    Gi1/0/2

otg#show 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       0047.6931.2f30.2f       Jan 09 2016 04:53 AM    Automatic
192.168.100.5       0047.6931.2f30.2f32     Infinite                Manual

As you can see above the dhcp server compares only 0047.6931.2f30.2f instead of 0047.6931.2f30.2f32 when connected to port 2 (Gi1/0/2). Thus a dynamic ip is assigned. Why is this the case? I am guessing since this field usually holds a mac address and this exceeds its max size thus information is lost.

Is there a way to manually assingn subscriber-id to an interface? If not how to make this work.

Link to instructions: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/security/configuration_guide/b_sec_152ex_2960-x_cg/b_sec_152ex_2960-x_cg_chapter_01101.html

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