How to Configure Microsoft Windows DHCP for Inter-VLAN Network Segments?

Figure 1: Network Diagram for Project

In this article we have been configuring Microsoft Windows DHCP for inter-VLAN network segments involves setting up separate DHCP scopes for each VLAN and enabling IP helpers on the Layer-3 Switch to relay DHCP requests from clients on different VLANs to the DHCP server. 

What is DHCP?

DHCP (Dynamic Host Configuration Protocol) is a protocol that provides quick, automatic, and central management for the distribution of IP addresses within a network. It’s also used to configure the subnet mask, default gateway, and DNS server information on the device.  

As shown in figure we will first of all make three VLAN’s 10,20 and 30 having name VLAN10, VLAN20 and VLAN30 respectively.  

                         Figure 2: VLAN Creation in Layer-3 Switch

 

Now we will give IP address to VLANS interfaces we have created in Layer-3 switch as shown in figure 2 to act as default gateway for inter-VLAN communication or routing, as shown in figure below.

Figure 3: IP assignment to VLAN interfaces

As IP has been assigned, we will assign ports to each VLAN for accessing and differentiating different networks. As three Layer-2 Switches are connected to three ports of Layer-3 switch (Core Switch) so these will act as different networks as shown below.

Figure 4: Port 1 to VLAN 10

Figure 5: Port 2to VLAN 20

Figure 6: Port 3to VLAN 30

After creating VLANS and assigning IP’s to interfaces we will create IP DHCP pools for these VLANS which will be used by Microsoft Server which act as DHCP server to assign IP addresses to hosts relevant to each VLAN were connected.

Figure 7: IP Pools in Window Server

As shown in figure above (figure 7) we have created/added three pools which will act as IP Pool for three different VLAN’s.

Now on Layer-3 Switch we will use one command ip helper-address<DHCP server IP> in every interface of VLAN we have created which enable hosts to get there IP address from there network range of DHCP Scope.

Figure 8: IP Helper Command for DHCP Relay in Layer-3 Switch

As shown in Figure Below hosts (PC’s) connected to layer-2 switches are assigned with IP addresses through DHCP configuration. The IP assignment has started from 192.168.10.2 because 192.168.10.1 acting as default gateway.

Figure 9: DHCP IP for VLAN 10

Figure 10: DHCP IP for VLAN 20

Figure 11: DHCP IP for VLAN 30

An IP helper-address, also known as a DHCP relay agent, this is a feature that forwards DHCP broadcast packets to a specific DHCP server on a different network segment. When a client device on a network segment requests an IP address through DHCP, it sends out a broadcast packet.