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Check if Your Device Support DHCP Option-82

 

To configure a switch with DHCP relay in forward-only mode, check whether your device supports DHCP Option 82.

Use the procedures in Table 1 to confirm the support of Option-82 or required workaround.

Table 1: Verify support of Option-82 in DHCP Server

Problem

How to Verify ?

Solution

Verify if your switching device supports DHCP Option 82.

Use the dhcp traceoptions on the DHCP Relay. A message states the drop due to missing Option 82.

If the DHCP Offer packet dropped because of Option-82 not included, you will receive the message like:

Feb 25 15:41:13.577519 [MSTR][NOTE] 
[default:default][RLY][INET][irb.6] 
jdhcpd_packet_handle: BOOTPREPLY could not find
client table entry

To fix the issue:

  • Solution 1: Upgrade the DHCP Server to Junos OS version that fully supports Option 82.

  • Solution 2: Change the DHCP Relay to a “stateful” mode (that is, DHCP Relay “binding” mode).

  • Solution 3: Move the DHCP Relay to a MX or to a non-ELS EX/QFX switch, so to enable the Legacy ‘helper bootp’ mode.