DHCPrelay can't receive reply from the server

[jgomez at infoweapons.com]

> jgomez at infoweapons.com wrote:
>
>>The client can't acquire an Ip address.. The relay agent can relay the
>>message to the server, but the the relay agent can't receive the reply
>>from the server.
>
>
>
>>Can anybody help me in finding what's the possible solution?
>
>
> Got wireshark or tcpdump installed ?
> If not, then that's your first step.
>
> Follow the packets and see where they are ACTUALLY going which may
> not be the same as where the logs show. You need to follow the
> packets and see where exactly they are stopping.
>
>
> Do you have any firewalls configured on these interfaces ? Are they
> configured to let the packets through ?
>
>
> Is your dhcp config right ? Post the whole file and we can look it
> over - I can see one thing wrong just in your extract which could be
> enough for a client to ignore an offer.
>
>


Hi guys!

 Simon, thanks to ur reply.. No firewalls configured on each interface.

i got it already.. ;)

There should be a 192.1.2.0 subnet in my dhcpd.conf since the client is
connected to 192.1.2.2 as shown the diagram below. (Previously, i only
have 128.1.2.0 subnet in my dhcpd.conf.)

               (em1)       (em1)
   +-------------+     192.1.2.2 +-------------+

   |  128.1.2.x  +---------------+ relay agent |

   +-------------+               +------+------+

                                        |   (em0)
                                        | 128.1.2.2
                                        |
                                        |
                                        |   (em0)
                                        | 128.1.2.1

                                  +-----+-------+

                                  | dhcp server |

                                  +-------------+

Because when a relay agent receives a message from a DHCP client on a
particular network segment(which in this case 192.1.2.2), it records the
IP address of the interface on which it received the request in the giaddr
field of the message, and then it forwards the message to the DHCP server.
The server uses the giaddr field to determine what network segment the
client is attached to. When it has a reply for the client, it sends the
reply back to the relay agent, using the Ip address the relay agent stored
in the giaddr field. the DHCP relay agent then sends the message back to
the client.

Now, in my dhcpd.conf i have:

subnet 128.1.2.0 netmask 255.255.255.0
{
  range 128.1.2.26 128.1.2.66;

}

subnet 192.1.2.0 netmask 255.255.255.0
{
   range 192.1.2.10 192.1.2.89;
}

the client did acquire an IP address of 192.1.2.89.

Jonna



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