[CentOS] CentOS-6 dhcpd

Les Mikesell lesmikesell at gmail.com
Fri Jul 15 22:30:37 UTC 2011

On 7/15/2011 3:53 PM, Ljubomir Ljubojevic wrote:
>>>>> and there is no mention of interfaces, just their IP's, and you can only
>>>>>     set DHCP service on the first IP on the interface.
>>>> What exactly do you mean when you say that "you can only set DHCP service
>>>> on the first IP on the interface"?
>>> I use ISC DHCP on non-CentOS router. On that router, ISC DHCP will not
>>> hand out IP addresses on second (or virtual eth0:0, eth0:1, ...) IP on
>>> the interface, just for the subnet original, true IP is set.
>>> Since ISC DHCP should be the same, this should be also true for CentOS
>>> version of ISC DHCP server.
>> Did you use a 'shared-network' declaration?  It still isn't going to be
>> able to distinguish which address range to give out to any particular
>> client unless you've specified the hardware ethernet for it, though.
> On the router I am using I guess that info is taken from the router it
> self. I just have to declare subnet and that is it. Routers always
> respond on any interface with first IP declared on that interface, and
> it is always with the first IP. Giving out IP is on the same principle,
> request comes on the interface and server queries first IP address of
> the interface and searches for the subnet.

No, it isn't quite the same.  The shared-network declaration should let 
dhcpd match up the physical interface with one of the subnets and 
associate all that are grouped.  But it may give out all of one range 
before starting on another in the group.

> But ones again, this is *not* on the CentOS, ISC DHCP version is newer
> (4.1.0) then in CentOS 5.6 (3.0.5),
> Here is config file and output of the server with only one active subnet
> declaration (and coincidence is it is with shared lan) on 5 interface
> router:
>        shared-network drlan {
>      subnet netmask { }
>      subnet netmask {
>         range;
>         option routers;
>      }

You only have one range, so it can't give out anything for the other subnet.

   Les Mikesell
    lesmikesell at gmail.com

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