Description

This article describes the issue of the DHCP relay server not generating the unicast message.

Symptoms

Normal Operation of DHCP Relay:

  1. A DHCP client (for example, a PC) broadcasts a DHCP Discover message.
  2. The SRX Series device converts this packet from broadcast to unicast.
  3. The DHCP server sends the DHCP Offer message back to the router as unicast.
  4. The SRX Series device converts the DHCP Offer message back to broadcast; which is sent out on the interface of the original device.  
In this case, the DHCP Relay device (i.e. SRX) is not generating the Unicast Message.

Solution

DHCP Traceoptions shows the following messages:

Nov 10 05:08:07 UI_CONFIGURATION_ERROR: Process: dhcpd, path: [edit system], statement: name-server, Invalid name-server value
Nov 10 05:08:12 UI_CONFIGURATION_ERROR: Process: dhcpd, path: [edit system], statement: name-server, Invalid name-server value

system {
    name-server {
        4.2.2.2;
            0.0.0.0;
    }
}

The DHCP Relay server needs to have the DNS configuration for the DHCP clients. In our Junos implementation, the DHCP daemon will read the DNS configuration and the daemon will quit when there is an Invalid DNS-Server value.

This inter-dependency is removed and the issue is resolved in 10.4R9.

Modification History

19-11-2025: Minor, non-technical edit