[CentOS] 2 DHCP servers - different VLAN's

Matt Shields matt at mattshields.org
Sat Jul 26 01:51:13 UTC 2008


On Fri, Jul 25, 2008 at 4:46 PM, David Hláčik <david at hlacik.eu> wrote:

> Hello  guys,
>
> to describe my scenario
>
> i have 4 VLANS on my switch, each VLAN is different subject. I have one
> DHCP server for 3 VLANS + second one DHCP server for 1 VLAN - named VLAN 7 .
>
> Problem is , this started to make problems suddenly. VLAN 7 is not
> recieving IP adress from correct DHCP server . On DHCP server where
> declaration for subnet is configured, i am recieving this message :
>
> Jul 25 12:38:47 boss dhcpd: DHCPNAK on 10.123.42.169 to 00:16:cf:93:1f:33
> via eth0
> Jul 25 12:38:52 boss dhcpd: DHCPREQUEST for 10.123.42.169 from
> 00:16:cf:93:1f:33 via eth0: wrong network.
>
> How can i solve it and what does it mean?
>
> I am using authoritative clausule in each subnet deffinition.
>
> Thanks in advance!
>
> David
>
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>
If VLAN 7 has access to the VLAN that the primary dhcp server is on, you
need to somehow block dhcp requests.  What I did was besides using VLAN's on
my switches, I have a Sonicwall firewall which handles the actual routing
between vlans, then I set certain vlans to use the first dhcp server via a
dhcp helper in the firewall.  Then in the other vlan I point the dhcp helper
at the second dhcp server.


-- 
-matt
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