DHCP: client-identifier/hardware-address

[michal.dudzak]

Hello,

iam using docking station which have its own network card and i would like to staticaly bind it to ip address. It should work as whenever i connect anything to docking station it should get same fixed IP address always. However it is not working like that.

every time i connect linux client it is tied to hardware address

every time i connect windows client it is tied to client-identifier

so when i configure static dhcp pool it is working only half way.

example:

ip dhcp pool DYNADOCK
host 10.10.1.101 255.255.255.0
hardware-address 0050.b656.49b5
default-router 10.10.1.1

 this is working only for linux

ip dhcp pool DYNADOCK
host 10.10.1.101 255.255.255.0
client-identifier 0100.50b6.5649.b5
default-router 10.10.1.1

this is working only for windows

is there any way to bypass this problem?

[Flavio Miranda]

Hello @michal.dudzak

This happen probably because Linux allows for a  much more deeper control level, whilst Windows dont.

For linux, you can tell the dhcp client to send the client identifier by editing dhcpclient.conf.

$ cat /etc/dhclient.conf
interface "eth0"
{
send dhcp-client-identifier 1:xx:xx:xx:xx:xx:xx;
send dhcp-lease-time 86400;
}

-If I helped you somehow, please, rate it as useful.-

[michal.dudzak]

iam sorry for late reaction i was too busy to answer, however i have tried proposed solution. I have not found anything like 

interface "eth0"
{
send dhcp-client-identifier 1:xx:xx:xx:xx:xx:xx;
send dhcp-lease-time 86400;
}

in my dhcpclient.conf.

Also adding those lines have no impact on cisco device. 

But i found GUI for changing settings of the network card (picture attached). I was able to send client-identifier via GUI to cisco device which finaly was succesfull and it worked.  However i have no idea which configuration file were changed and i would be glad to know that. (dhclient.conf remain untouched by it)

[Francesco Molino]

Hi
Can you check the file /etc/network/interfaces
Is that one changed and what was added?

[michal.dudzak]

hello,

there is nothing in that file beside this:

auto lo
iface lo inet loopback

any other ideas? :)

distro is Kali Linux 

[Flavio Miranda]

Hi @michal.dudzak

 I have a Cali right here in front of me and I can see this under /etc/dhcp/

Take a look on the pic attached.

-If I helped you somehow, please, rate it as useful.-

[Francesco Molino]

Hi

On the Cisco side, there is nothing that you can do. However, on Linux machine, you can modify dhclient.conf to send the client-identifier.
This command can be adapted to use a variable as hardware will be different from on or out of docking station.

[michal.dudzak]

thank you guys iam going to try this after work tommorow and let you know

[Austin Sabio]

I am not sure if I am following here but I would suggest to make an ip reservation through dhcp server if applicable as long as the mac address is identified. 

I hope this helps. Good luck!