This article describes how to configure an SRX device as a Relay Agent, using the JDHCP feature (supported by JunosV App Engine 12.x or later releases).

Starting with JunosV App Engine 12.x, the DHCP process has been modified and the new process is JDHCP. Even though both processes run on the SRX, it is recommended to use JDHCP and not DHCP.

Setup:                                              

                                                           
  dhcp-clients -----------ge-0/0/1.0 -SRX--ge-0/0/0.0 ---------------------DHCP Server

Relay interface is ge-0/0/1.0
DHCP server facing interface is ge-0/0/0.0

Both interfaces are in dhcp-relay custom virtual router.

Configuration:                

1. Configure DHCP server address:
set routing-instances dhcp-relay forwarding-options dhcp-relay server-group wifi-server 192.168.1.254


2. Activate the server:
set routing-instances dhcp-relay forwarding-options dhcp-relay active-server-group wifi-server


3. Configure relay interface:
set routing-instances dhcp-relay forwarding-options dhcp-relay group relay-in-vr interface ge-0/0/1.0

Verification:

1. Use this command to check the statistics related to the DHCP protocol:
   
root@vsrx-1# run show dhcp relay statistics routing-instance dhcp-relay
Packets dropped:
Total 0

Messages received:
BOOTREQUEST 67
DHCPDECLINE 0
DHCPDISCOVER 38
DHCPINFORM 0
DHCPRELEASE 0
DHCPREQUEST 29

Messages sent:
BOOTREPLY 3
DHCPOFFER 1
DHCPACK 1
DHCPNAK 1
DHCPFORCERENEW 0
 
2. Use this command to check the IP addresses assigned to client via configured dhcp-relay:
   
root@vsrx-1# run show dhcp relay binding routing-instance dhcp-relay

IP address      Session Id       Hardware address      Expires       State            Interface
10.10.10.2           8                   00:0c:29:e9:6d:00         85624       BOUND       ge-0/0/1.0

Note: Dhcp-Relay feature in chassis cluster is supported from Junos OS 12.1X46D10. 

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