DHCP options

Simon Hobson dhcp1 at thehobsons.co.uk
Mon Apr 4 08:13:44 UTC 2011

Moayad Mohammad wrote:

>I have DHCP server (dhcp-3.0.5-23.el5_5.2) on 
>linux server, this DHCP server assign dynamic 
>IP's for our WiMAX customers.
>The WiMAX CPE connected directly to PC/laptop/Wireless route etcŠ
>I want to assign static IP for any device 
>connected to the WiMAX CPE even the customer 
>change his device without asking for the MAC 
>address for the device and he change his device.

That version is fairly old now, you might want to 
be looking at an upgrade sometime.

Your fundamental problem is that you need a 
unique and persistent identifier for the client. 
BY default this is the client-id, or if this is 
not supplied by the client (as is the case for 
most non-WIndows devices), the MAC address. 
Unless you have something else then you are stuck 
with the MAC address.

In some networks it's common to use option 82, 
Circuit ID, for an alternative identifier. This 
is inserted into client requests by the switch or 
cable network equipment, and can be used to 
assign addresses to clients (with some effort).

If your network can identify clients by an 
equivalent to Option 82 (as might be the case if 
you have an NTE at the client end into which the 
client connects his equipment) then you may want 
to search the archives for Option 82. Otherwise I 
think you're stuck with MAC address.

Simon Hobson

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