DHCP Help Wanted

[TheKnat]

The network at my new company is setup a bit strangely, so I thought I'd ask for some help. The network is split over two sites, which have 2 very different subnets being used (no idea why) with a 10Mb link between the two. The first site has a DHCP server which serves its clients fine. The second site doesn't have a DHCP server so all the clients are setup on static IP adddresses.

Now I want to set a DHCP server up on the second site, but because of the different subnets they use, I have to make sure that none of the clients in site 1 can get an ip address from dhcp server 2.

Is there a way I can manually check if DHCP can get over the link (apart from plugging in a computer at site 2) ? If the DHCP requests can get over the link, is there a way to make the server on the local site more likely to get the requests ?

I've done this before using 2 different VLANs to separate out the IP addresses given to clients, but I don't think they have the neccesary hardware to do this.

 

[Chief Wiggum]

Hi there,

DHCP requests can't cross a routed boundry by default as they're broadcasts. The only way this can happen is by turning it into a unicast transaction.

On cisco gear you do this with a DHCP helper command and specify the DHCP server that you want to talk to.

So in short - DHCP requests won'tt cross into the other site if you're using routers (or Layer 3 switches to route)

Kev

 

[TheKnat]

Just the answer I wanted thanks. Although our network gear is rubbish, I beleive the the 2 BT routers that were put in with the link are quite decent so they are probably going to block the DHCP requests going through it.

Looks like I just need to install the other DHCP server and watch the magic happen.