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[MX] Devices connected to MX router fails to receive IP address through DHCP operation

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Article ID: KB35608 KB Last Updated: 27 Mar 2020Version: 1.0
Summary:

DHCP service enabled on a MX router blocks legacy bootp operation.

Symptoms:

Devices/Clients connected to MX router fails to receive IP address through DHCP operation. MX router plays the role of the DHCP relay agent.

Outputs in the broken state: 

show dhcp statistics 
Packets dropped:
    Total                      0

Traceoption file configured for helper process returned the following log message: 

FUD_BIND_FAILURE: bind(port 67) failed: Address already in use

The above message indicates that the binding is failing as port 67 is already being used by the locally configured DHCP service.

Cause:

DHCP service / traceoptions enabled on the MX router blocks port number 67 for use by the legacy bootp process.

Solution:

Disabling DHCP service/traceoptions on the MX router resolves the issue. The following command can be used to disable any dhcp-service traceoptions configured as well:

set system processes dhcp-service disable   
Example output in the working state:
show dhcp statistics 
warning: dhcp-service subsystem has been disabled by the user

show system processes extensive | match dhcp  <-- DHCP daemon no longer running on the device.

show system processes extensive | match helper  
6284 root      52    0 39572K  1928K wait    2   0:00   0.00% jlaunchhelperd  <-- helper process is now running on the device
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