NSX-T 3.1 – Configuring DHCP Server

As I build out various demonstrations in my lab I wanted to reduce the amount of static IP allocations on my demo work loads so that I can move them between network segments for different demonstrations and with this enabling a DHCP Server in my NSX-T deployment makes sense.

So in this post I will cover the steps and procedure to follow enabling DHCP on my Local NSX-T Manager.

Overview

DHCP (Dynamic Host Configuration Protocol) allows clients to automatically obtain network configuration, such as IP address, subnet mask, default gateway, and DNS configuration, from a DHCP server.

As per VMware documentation, NSX-T Data Center supports three types of DHCP on a segment:

  • DHCP local server
  • Gateway DHCP
  • DHCP relay.

DHCP Local Server
As the name suggests, it is a DHCP server that is local to the segment and not available to the other segments in the network. A local DHCP server provides a dynamic IP assignment service only to the VMs that are attached to the segment. The IP address of a local DHCP server must be in the subnet that is configured on the segment.
Gateway DHCP
It is analogous to a central DHCP service that dynamically assigns IP and other network configuration to the VMs on all the segments that are connected to the gateway and using Gateway DHCP. Depending on the type of DHCP profile you attach to the gateway, you can configure a Gateway DHCP server or a Gateway DHCP relay on the segment. By default, segments that are connected to a tier-1 or tier-0 gateway use Gateway DHCP. The IP address of a Gateway DHCP server can be different from the subnets that are configured in the segments.
DHCP Relay
It is a DHCP relay service that is local to the segment and not available to the other segments in the network. The DHCP relay service relays the DHCP requests of the VMs that are attached to the segment to the remote DHCP servers. The remote DHCP servers can be in any subnet, outside the SDDC, or in the physical network.


You can configure DHCP on each segment regardless of whether the segment is connected to a gateway. Both DHCP for IPv4 (DHCPv4) and DHCP for IPv6 (DHCPv6) servers are supported.

For a gateway-connected segment, all the three DHCP types are supported. However, Gateway DHCP is supported only in the IPv4 subnet of a segment.

For a standalone segment that is not connected to a gateway, only local DHCP server is supported.

Assumptions

My base networking has already been configured and deployed and I will address enabling the DHCP services on one segment which I want to allocate Private IP’s too and translate these with Source based NAT to provide Internet access to this segment.

Configuration

For the purpose of this demonstration which I am working on, I will configure a DHCP Local Server on my segment with network range 10.10.10.0/24. My T1 default gateway is 10.10.10.1.

Step 1 – Create a DHCP Profile

You can create DHCP servers to service DHCP requests from VMs that are connected to logical switches.

Select Networking > DHCP > ADD DHCP Profile> Add.

Adding a DHCP Profile
  • Enter a Profile name = DHCP-LM-DC-01
  • Profile Type (DHCP Server / DHCP Relay) = DHCP Server
  • Enter the IP address of the DHCP server and its subnet mask in CIDR format: 192.168.10.240/24
  • Lease Time (Should be between 60 and 4294967295): Default is 84600
  • Select the Edge Cluster: LM-EDGE-Cluster-DC-01
  • Select the Edge(s): edge-dc-03 for my lab
Selecting edge-dc-03 from my Edge Cluster

Once all the fields are populated, hit save

DHCP Profile populated data

Step 2 – Attach a DHCP Server to a Segment

Networking > Segments > Select Segment

Configure a new segment or select the one you want to edit, in my case I will edit DC-01-NAT-Segment

Edit Segment to Set DHCP Config

SET DHCP CONIFG

Blank DHCP Settings

Now we need to populate the details and select the options matching our requirements.

  • DHCP TYPE: LOCAL DHCP Server
  • DHCP Profile: DHCP-LM-DC-01
  • IP Server Settings:
    • DHCP Config: Enable
    • DHCP Server IP Address: 10.10.10.254/24
  • DHCP Ranges: 10.10.10.10-10.10.10.100
  • Lease Time (seconds): 3600
  • DNS Servers: 192.168.10.5
DHCP Configurations Populated in the UI

APPLY and SAVE.

Step 3 – Attach Virtual Machine to the Network and set networking settings to DHCP

Setting my VM to obtain an IP via DHCP

The virtual machine has succesfully obtain a dynamic IP address from the DHCP Server created in NSX-T

Dynamic IP 10.10.10.10 allocated via DHCP seen in vCenter
DHCP IP allocated to the Virtual Machine from 10.10.10.254
Final Topology with DHCP and NAT enabled

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