DHCP server behing Cisco relay

[Hernan Saltiel]

Hi José,

   Today, I have a Windows machine running a DHCP server, with IP address
192.168.120.20/24, and serving DHCP address range 10.0.0.10 ->
10.0.200.200. Then, I can assume that my Cisco switch is working just fine.
It's a soho switch, so it has only "secondary subnets", a concept that may
sound like vlans, but are not. But this is working fine.

   Thanks, and best regards,

HeCSa.



On Fri, May 20, 2016 at 6:46 PM, José Queiroz <zekkerj at gmail.com> wrote:

> Hi Hernan,
>
> Could you please post the Cisco Switch's relevant configuration, also?
> Including the VLAN interfaces serving the 10.0.0.0/16 network.
>
> By the way, does this switch have conectivity with your dhcp server? This
> is mandatory for the DHCP relay to work, as the relay agent needs to
> forward DHCP messages for clients in unicast to the DHCP server; and the
> reverse path must be available also, once you're checking the direct path,
> give some time checking this also.
>
>
> 2016-05-20 17:58 GMT-03:00 Hernan Saltiel <hsaltiel at gmail.com>:
>
>> Hi everybody.
>>
>> Maybe I'm asking something previously answered.
>> I configured my new iscp-dhcp-server (Ubuntu 16.04) to server requests
>> from a network of APs.
>> Those APs are connected to a Cisco switch, having 192.168.120.1/24 as
>> primary address, and a secondary subnet with address 10.0.0.1/16 (yes,
>> 16...). It has relay configured, just to send the dhcp requests to
>> 192.168.120.20, a Windows machine.
>> Today I have a Windows machine connected there, where I use the AP
>> controller software, and TFTPD64, a thin software that works as a DHCP
>> server. I configured there a range (10.0.0.10 -> 10.0.200.200) and
>> everything works well, but it's Windows, then from time to time, I have to
>> reboot the system.
>> This is why I configured the new machine as 192.168.120.40/24, installed
>> isc-dhcp-server package, and configured the following lines on
>> /etc/dhcp/dhcpd.conf:
>>
>> default lease-time 600;
>> max-lease-time 7200;
>>
>> subnet 10.0.0.0 netmask 255.255.0.0 {
>>   range 10.0.0.10 10.0.200.200;
>>   option subnet-mask 255.255.0.0;
>>   option routers 10.0.0.1;
>>   option domain-name-servers 8.8.8.8, 8.8.4.4;
>> }
>>
>> subnet 192.168.120.0 netmask 255.255.255.0 {
>> }
>>
>> When I start the server, I only see it trying to answer requests using
>> network 192.168.120.0, then saying "no free leases", and not serving any
>> 10.0.0.0/16 address.
>>
>> Now I'm living with TFTPD64, but I plan to move that to a better solution.
>> Does anybody know about this configuration? Is there something I'm doing
>> wrong?
>> Thanks a lot in advance, and best regards.
>>
>> --
>> HeCSa
>>
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>
>
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-- 
HeCSa
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