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 :
otg#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
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.
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