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How to Configure a DHCP Relay

This chapter provides information about configuring the Dynamic Host Configuration Protocol (DHCP) relay for a Juniper Mist™ Edge appliance.

DHCP Relay Overview

In a Juniper Mist™ network, the DHCP client-server protocol provides IP hosts with IP addresses and other related configuration information automatically. A DHCP relay (agent) is a host that sends DHCP packets between clients and servers that are not on the same physical subnet.

When a wireless client associates with a tunneled wireless LAN (WLAN) on Juniper Mist access points (APs), all the data packets from the wireless client are tunneled to the Juniper Mist Edge appliance. The tunneling occurs through the downstream ports. Thereafter, the Juniper Mist Edge appliance bridges all the data packets, including the DHCP packets. The appliance bridges the packets from the tunneled VLAN to the upstream infrastructure,

Note:

The DHCP relay function on Juniper Mist Edge supports IPv4 traffic only

The following image illustrates the client traffic flow between a Juniper Mist Edge appliance and a DHCP server:

Configure a DHCP Relay on a Juniper Mist Edge

Before you can configure a DHCP relay, the tunnel between the Juniper Mist access point (AP) and Juniper Mist Edge must be up and running. See Deploy Juniper Mist Edge at the Organization Level.

You also need the following information:

  • IP address of the DHCP server

  • VLAN ID and IP address

  • Route(IP address) to reach the DHCP server

To configure a DHCP relay on a Juniper Mist Edge appliance:

  1. On the Mist Edge Inventory page, select the Mist Edge appliance.
  2. In the DHCP Relay pane, select the Configure DHCP Relay check box.
  3. In the DHCP Relay pane, select the VLAN tab, and then click Add VLAN.
  4. Enter the VLAN ID, Netmask, and IP Address, and then click the blue check mark to save.
    This step creates a switch virtual interface (SVI) on the tunnel interface.
  5. In the DHCP Relay window, select the DHCP Server tab.
  6. In the Servers field, enter the DHCP Server IP addresses. Insert a comma to separate IP addresses.
    Note:

    This DHCP server list is common across all the wireless client VLANs configured for the DHCP relay.
  7. In the DHCP Relay window, select the Extra Routes tab, and then click Add Route.
    Note:

    • If you do not specify a route, Juniper Mist Edge uses the default route of the tunnel interface.

    • If you specify a route, the next hop must be in the same subnet as one of the relayed VLANs.
  8. Enter the destination addresses in the Host/Subnet field and the next hop address in the Next hop field. Then, click the blue check mark to save.
  9. On the Juniper Mist Edge page, click Save.

Configure a DHCP Relay Using the API

In addition to configuring a Dynamic Host Configuration Protocol (DHCP) relay through the Juniper Mist portal, you can configure the DHCP relay on your Juniper Mist Edge appliance using the API.

This is the API endpoint: /api/v1/orgs/{{org id}}/mxedges/{{MistEdge id}}.

The following output shows the API payload: