DHCPD broadcast question

Dear all,

I have trying to write a program to detect the dhcpd broadcasting. I am
able to detect the client's broadcasting by listening to port 67. But I
couldn't get anything from port 68.

Is there anything that I need to set for the DHCPD to use port 68 to
broadcast, also, which broadcast ip address would be used?

My program is currently listening to 255.255.255.0

Thx

(E-Mail Removed) wrote:
> I have trying to write a program to detect the dhcpd broadcasting.
> My program is currently listening to 255.255.255.0

255.255.255.255

Chris

In article <(E-Mail Removed) .com>,
(E-Mail Removed) wrote:

>I have trying to write a program to detect the dhcpd broadcasting. I am
>able to detect the client's broadcasting by listening to port 67. But I
>couldn't get anything from port 68.

See RFC2131 Section 4.1

NORMALLY client to server is broadcast to port 67, because the client
doesn't know either address. The server monocasts to port 68.

0.0.0.0:1025 -> 255.255.255.255:67

IP.OF.SERV.ER:3456 -> IP.OF.CLI.ENT:68

Remember, this is Ethernet, so the packet at that level looks like

MA:CAD:RE:SS:Client -> FF:FF:FF:FF:FF:FF

Server:MA:CAD:RE:SS -> MA:CAD:RE:SS:Client

Now, if you are on a 'switched' network (rather than a hub or coax),
the switch probably won't spray the reply out all ports - you won't hear
it, unless you are on a common switch port.

Old guy