Troubleshooting DHCP issues
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Restrictive firewall issue
DHCP will not work if outgoing packets to UDP port 67 are not allowed in firewall. In such cases messages:
Failed to send 300 byte long packet over fallback interface
might get appended to /var/log/messages and monitoring systems should pick up these as unknown message. The problem can be easily resolved by updating firewall to allow outgoing packets to UDP port 67.
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