Old Tired Question: 'Not configured to listen on any interfaces'

[Simon Hobson]

Alex Bligh wrote:

>>>You can use a 0.0.0.0/0 subnet without complaint.
>>
>>And you would struggle to be more wrong in doing so.
>>
>>That would tell the DHCP server that the entire IPv4 address space is
>>directly connected to that interface. So when it gets a request from
>>*anywhere* there is confusion as to where the client is located.
>
>The OP was only using dhcpd as a target of a relay. In this instance the
>IPv4 space is *not* connected to the interface, but dhcpd essentially won't
>hand out IP addresses until it thinks it is on a subnet it knows about. Our
>server (which only gets relay requests) needs to return arbitrary dhcp
>replies, all of which need to be within a subnet dhcp knows about. dhcpd
>trying to know about the subnet structure is in fact unhelpful, which I
>thought what the OP was saying, not least because the subnet structure wuld
>have to follow our DB (when this is unnecessary). So we use a config like
>the following (well, in fact identical to the following bar the password
>etc changes). dhcpd thinks the entire IP address range is one subnet, but
>as all the subnet has to do is *include* anything we return, this is fine.

OK, so in YOUR case you've made a broken config work for you. It will 
**NOT** work if you (as is the norm for most people) have dynamic 
address pools and multiple connected subnets - the server WILL get 
confused.
It's working for you because you don't use the dynamic part of DHCP. 
Your setup is quite uncommon, and you have effectively offloaded 
**ALL** the subnet selection logic to whatever maintains your 
database.

Just out of interest, what happens to mobile clients - or don't you have any ?
-- 
Simon Hobson

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