[CentOS] CentOs 6 DHCP Server and virtual interface

Johnny Hughes johnny at centos.org
Mon Feb 4 11:42:59 UTC 2013


On 02/03/2013 08:11 AM, Grzegorz Sołtys wrote:
> So, if my WAN IP adress is 83.238.*.* then i need to run DHCP server
> in the same class of if address. But, if got only this address and i
> will setup in eg: 83.238.55.10 to 15 range for eth0:0 and there is a
> machine with WAN address like 83.238.55.13 if gonna to make IP address
> colission? or then it will be avalible only as LAN Address for my server?
>

Yes, if you are going to serve dhcp to a subnet, the server has to have
an address on that subnet.  It will indeed need to take one of the
addresses of that subnet, and you can not have one of your other
machines get that address.

You can use the dhcp machine to do other things on that same address
though ... so it can do dhcp AND replace one of the other machines.


> W dniu 2013-02-03 14:50, Johnny Hughes pisze:
>> On 02/03/2013 07:38 AM, Grzegorz Sołtys wrote:
>>> I have made it, and the DHCP server won't start telling me:
>>>
>>> " Feb  3 13:42:21 vlan19 dhcpd: No subnet declaration for eth0:0 (no
>>> IPv4 addresse s).
>>> Feb  3 13:42:21 vlan19 dhcpd: ** Ignoring requests on eth0:0.  If this
>>> is not what
>>> Feb  3 13:42:21 vlan19 dhcpd:    you want, please write a subnet
>>> declaration
>>> Feb  3 13:42:21 vlan19 dhcpd:    in your dhcpd.conf file for the
>>> network segment
>>> Feb  3 13:42:21 vlan19 dhcpd:    to which interface eth0:0 is
>>> attached. **
>>> "
>>>
>>> I have conifgured all files to use DHCPD on this interface.  Do you
>>> need all conifguraiton?
>> Inside your dhcpd.conf file you need a subnet declaration and the IP
>> Address of ETH0:0 has to be in that subnet.
>>
>> See:
>>
>> https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sect-Configuring_a_Multihomed_DHCP_Server.html
>>
>>
>>
>> So, for example, if I have:
>>
>> subnet 192.168.0.16 mask 255.255.255.240 {
>> option <whatever>
>> option <whatever2>
>> }
>>
>> Then eth0:0 would have to be inside the IP Range of the subnet ... in
>> this case, 192.168.0.16/255.255.255.240 is the IP addresses from
>> 192.168.0.16 through 192.168.0.31 (with 16 and 31 being not usable as
>> they are the network name and the broadcast address).  This would mean
>> that eth0:0's IP address would need to be somewhere in the range of
>> 192.168.0.17 and 192.168.0.30 to serve that subnet.
>>
>>> W dniu 2013-02-03 14:28, Johnny Hughes pisze:
>>>> On 02/03/2013 06:38 AM, Grzegorz Sołtys wrote:
>>>>> Hello All
>>>>>
>>>>> I have looking for any specific answer for one thing.
>>>>>
>>>>> I have a virtualized Server with only one physical interface eth0
>>>>> (WAN).
>>>>> To run OpenVPN i need to use DHCP server. And here is the
>>>>> question: is
>>>>> there a chance to run DHCP server on eth0:0 interface? Or it is
>>>>> impossible ?
>>>>>
>>>>> Thanks in advance.
>>>>>
>>>>   From the EL6 Deployemtn Guide:
>>>> https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sect-Configuring_a_Multihomed_DHCP_Server.html
>>>>
>>>>
>>>>
>>>>
>>>> "If a system has three network interfaces cards -- eth0, eth1, and
>>>> eth2
>>>> -- and it is only desired that the DHCP daemon listens on eth0, then
>>>> only specify eth0 in /etc/sysconfig/dhcpd"
>>>> DHCPDARGS="eth0"
>>>>
>>>> So in your case, edit the file /etc/sysconfig/dhcpd and set:
>>>>
>>>> DHCPDARGS="eth0:0";
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>
>>
>>
>>
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>
>


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