ISC DHCP server ignores fixed address specification for Circuit-ID

[codedd713]

Hi Team,

I observed this behavior (below) on ISC DHCP server. Was wondering if this is to be expected or perhaps I overlooked some element.

If a Fixed Address for a Circuit-ID value exists in the DHCP client’s *giaddr* subnet, and if the MAC address or Client Identifier of a DHCP client has a Host/Fixed-Address specification in any other subnet, DHCP server ignores the Fixed Address statement for Circuit-ID in *giadder’s* subnet and looks to provide a free IP within the *giaddr’s* subnet

Test done:

1. Deploy ISC DHCP server version 4.3.5

2. Create and assign the below objects to server:

Network:  192.168.5.0/24

                 Fixed Address:  192.168.5.111 – Circuit-ID: 74:65:73:74

                Range:  192.168.5.200  –  192.168.5.250

Network:  10.1.1.0/24

                Fixed Address:  10.1.1.11 – MAC: aa:aa:aa:aa:aa:aa

dhcpd.conf

subnet 192.168.5.0 netmask 255.255.255.0 {

        host 192.168.5.99 {

                dynamic;

                host-identifier option agent.circuit-id 74:65:73:74;           <-- Hex value for the word -  test

                fixed-address 192.168.5.99;

        }

        range 192.168.5.10 192.168.5.50;                     <-- or any possible range with free IP addresses

}

subnet 10.1.1.0 netmask 255.255.255.0 {

        host 10.1.1.11 {

                dynamic;

                hardware ethernet aa:aa:aa:aa:aa:aa;

                fixed-address 10.1.1.11;

        }

}

3. Using DHCP client simulator, send DISCOVER packet to server with below parameters:

                Client MAC address: aa:aa:aa:aa:aa:aa

                Relay agent IP address: 192.168.5.1

                Agent Circuit ID: test       <-- Hex : 74:65:73:74

Outcome:

 On receiving the DHCP DISCOVER packet, server OFFERs IP address  192.168.5.50               <--  from subnet's range  192.168.5.10 - 192.168.5.50 , rather than from fixed-address

4. Remove fixed-address 10.1.1.11 for Ethernet address aa:aa:aa:aa:aa:aa . Repeat DHCP DORA with same parameters

Outcome:

 Server OFFERs correct IP address  192.168.5.99                   <-- from fixed-address for the Circuit-ID in subnet

Any input is much appreciated.

Best Regards,
Edward

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