Multiple DHCP servers on one network. 1

[Kman0375]

I have 2 DHCP servers on 2 different subnets each subnet is on its own hub. we have 1 T-1 line and a Cisco 2500 router that has 2 different gateways programed into it. the router has only 1 ethernet port and we need the T-1 to go to both subnets. If we put a ethernet link between the two hubs then the DHCP servers start giving the wrong addresses to the wrong computers. What kind of device can I use to remedy this?

 

[ShackDaddy]

Don't just put a cable between the two hubs, because then you join the two collision domains, or layer 2 networks. Layer 2 is where DHCP listens, and that's why you are having problems.

To be honest, the best thing you could do would be to get rid of one of your DHCP servers. A single DHCP server could serve both subnets, and would provide unique information to each of the subnets if you set the options on a per-scope level. The only other thing I can think of is installing a switch instead of a hub, and creating a VLAN on it that lets both subnets see the router, but not each other. The port that goes to the router would be part of both VLANs.

ShackDaddy

 

[Kman0375]

I can't get rid of one of the servers so a switch is the idea I'd go for. What kind of switch do you sugest?

 

[ShackDaddy]

Gosh, it depends what your needs are. If you would like to have some available switch ports for both of your subnets, you could get a 2900 series Cisco Catalyst switch, which usually go for around $600 these days (i think). Then separate it into two VLANs, with the port going to the router configured to be a member of both VLANs. Sort of a 'router on a stick' configuration.

You could also find an inexpensive 8-port switch, but whatever you get needs to support VLANs.

ShackDaddy