DHCP gives an IP when the DHCP relay is not in the subnet

[Eugene Grosbein]

06.01.2017 0:36, Mik J wrote:
> Hello,
>
> Is it possible that the dhcp offers an IP but the dhcp relay is not in the subnet ?
>
> I have a vlan 192.168.1.0/24 and 3 dhcp relay. Each dhcp relay will use a loopback to relay the dhcp request 10.1.1.1 or 10.1.1.2 or 10.1.1.3. The client machines will receive an IP in 192.168.1.0/24
>
> Is it possible ?
>
> NB: if there's a DHCP relay in 10.1.1.4, I don't want to offer an IP in 192.168.1.0/24
>
> Do you have a link or keywords that would help to find the typical configuration for that
>
> Thank you

I have same configuration and this works for me:

shared-network HotSpot {

   # DHCP relay addresses
   subnet 10.1.1.0 netmask 255.255.255.252 { deny unknown-clients; }
   subnet 10.2.1.1 netmask 255.255.255.255 {}

   # DHCP clients
    subnet 192.168.6.0 netmask 255.255.255.0 {
      option routers 192.168.6.1;
      option broadcast-address 192.168.6.255;
    }
}