dhcp server returns core dump when i define network with mask 8

jb jb.1234abcd at gmail.com
Tue Jul 23 12:38:15 UTC 2013

s m <sam.gh1986 <at> gmail.com> writes:

> and thank you jb but if i define my network like below,  server runs
> correctly:
> log-facility local7;
> subnet netmask {
>     range;
> }
> i think is reserved for broadcast too. is it not true? if
> yes, why dhcp server works correctly?
> please help me to clear my mind.
> regards,

Regarding subnets: netmask
is equivalent to
which splits it into a network id 192.168. and host id .0.0
Another example: netmask
is equivalent to
which splits it into a network id 192. and host id 168.0.0

Regarding broadcast address:

yes, for subnet the broadcast ip is .
What are the implications of including broadcast ip in range option ?

Firstly, it depends on how the authors of software, that is DHCP server,
interpreted the dhcpd.conf option data. They could have rejected that
option up front, or accept it (implying you are the boos !).
After all, dhcpd.conf(5) only says:
The range statement
range [ dynamic-bootp ] low-address [ high-address];
For any subnet on which addresses will be assigned dynamically, there
must be at least one range statement. The range statement gives
the lowest and highest IP addresses in a range. All IP addresses in
the range should be in the subnet in which the range statement is declared.
Well, looks good to me so far !

Next, dhcpd.conf(5) describes how DHCP server deals with:
You can analyse it and see if any trouble lurks there ...

Secondly, let's assume there was no problem and that ip was dispensed to a host.

But, in a different place of IP specs there is a RFC??? which says that
the as a generically valid ip address will assume some
additional meaning, that is it will be treated as a broadcast address
(it will represent all hosts on a subnet).
Wow ! That should give you a pause ...

It is said that the broadcast address is used by an application to send
the same message to all other hosts in the network simultaneously.
Who is using it ?

Well, our client host is using it (let's assume it was assigned that ip
above ...).
What happens when the host sends a packet out with a source ip address of
a broadcast ip address ? One can imagine that the destination host will
respond and send back a packet to a destination ip address which is our
sender's broadcast ip address ... You mean to every host on that network ?
Something fishy is on the way ...
But while doing it, it will utilize some protocols, like ARP, RIP, etc.

In addition, it is said that broadcast messages are typically produced by
network protocols such as the Address Resolution Protocol (ARP) and
the Routing Information Protocol (RIP).
They will utilize that ip broadcast address regardless of the fact that it
has been presumably assigned to the client host too.

Wow, what a soup ...
Enjoy it while it lasts :-)

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