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In a VMware ESXi 4.1 lab environment*, I have a pair of virtual networks configured (10.0.4.x and 10.0.10.x).

On both networks is a DHCP server.

The problem is that the networks are routable to each other, and VMs on the 10.0.10.x network sometimes get addresses from the 10.0.4.x dhcpd.

Is there a way to fix this behavior and give priority to the dhcpd on the 10.0.10.x network?


*I don't have administrative or networking privileges to change the host

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2 Answers 2

up vote 5 down vote accepted

This sounds like a network mis-configuration, plain and simple. "networks that are routable to each other" typically means there is a router in between them, whose job is to filter stuff like DHCP. If systems on one network are getting addresses from the DHCP server that is supposed to be on the other network, then either the router is forwarding DHCP between the networks, or, more likely, the networks are connected in a way that they shouldn't be.

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we did need to eventually engage the network team on this - the individual VLANs had been "paired" (according to the admin). That has been rectified, and we're good again. –  warren Mar 28 '12 at 12:57

A DHCP server has what is known as a scope: the networks from which it will dole out IP addresses. This usually (but not always) consists of the network it is itself connected to.

In your case, it sounds as if both DHCP servers can serve IPs on both networks. This is bad configuration; they should each serve only their own network.

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they are only handing-out addresses in their own scope (10.0.10.x and 10.0.4.x, respectively); the problem is that the virtual networks can see each other, so the 10.0.4 daemon often returns before the 10.0.10 daemon –  warren Mar 27 '12 at 17:10
1  
They should not "see" each other. –  adaptr Mar 28 '12 at 8:05

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