DHCP server behing Cisco relay

[José Queiroz]

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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