cancel
Showing results for 
Search instead for 
Did you mean: 

DHCP strange issues.

Community Veteran
Posts: 1,236
Registered: 02-08-2007

DHCP strange issues.

I have a network spanning two locations with a wireless bridge. Each location has an internet connection which is dished out by a dhcp server on each side for any machine without a static ip. A Talk Talk wireless router on one side and a Cisco 2611 on the other side provide DHCP. The same network exists on both sides with just a split in IP addresses in each DHCP server.
To make sure each side is assigned the correct IP / gateway / dns info, the wireless access point on my side of the network is firewalled through iptables on my CentOS fileserver. This blocks ports 67 and 68. This system worked perfectly up until recently.
Now at this end of the network (with the Cisco) IP and gateway info is provided by the Cisco every time as it should be but sometimes DNS info is received from the router on the other end which should be firewalled. This is irritating as local dns is used at this end for access to local resources.
How can a computer receive ip and gateway info from one dhcp server but dns info from another?
There are a things that have changed before I started to see this issue. The fileserver was reinstalled but the iptables config was saved first and reused. Also the Cisco 2611 used to be a Cisco 837 but again the config is exactly the same as before regarding the dhcp settings.
2 REPLIES
Community Veteran
Posts: 4,729
Registered: 04-04-2007

Re: DHCP strange issues.

Odd. Are you blocking  UDP packets on those ports?
Community Veteran
Posts: 1,236
Registered: 02-08-2007

Re: DHCP strange issues.

Yes, UDP and TCP just to be sure.