This article explains what the reason could be if you see the logs flooded with the following messages-

Jan 17 05:18:02.554 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.101 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:04.970 router1 kernel: %KERN-4: tcp_auth_ok: Packet from 192.168.1.9:39060 missing MD5 digest
Jan 17 05:18:06.561 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.102 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:07.007 router1 kernel: %KERN-4: tcp_auth_ok: Packet from 192.168.1.9:39060 missing MD5 digest
Jan 17 05:18:10.565 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.103 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:10.838 router1 kernel: %KERN-4: tcp_auth_ok: Packet from 192.168.1.9:39060 missing MD5 digest
Jan 17 05:18:12.144 router1 rpd[30830]: %DAEMON-4: bgp_get_open: peer 172.16.32.17 (External AS 137821): Reserved AS_TRANS(23456) cannot be used as the AS of any BGP Speaker (Used for 4 byte AS extension only)
Jan 17 05:18:12.144 router1 rpd[30830]: %DAEMON-4: bgp_get_open:3971: NOTIFICATION sent to 172.16.32.17 (External AS 137821): code 2 (Open Message Error) subcode 2 (bad peer AS number)
Jan 17 05:18:14.571 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.104 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:18.589 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.105 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:18.906 router1 kernel: %KERN-4: tcp_auth_ok: Packet from 192.168.1.9:39060 missing MD5 digest
Jan 17 05:18:22.602 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.106 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:26.610 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.107 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:30.617 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.300 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:34.622 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.310 configuration write failed for an IFL ADD: File exists
Jan 17 05:18:38.643 router1 dcd[30867]: %DAEMON-3-DCD_CONFIG_WRITE_FAILED: IFL ge-4/3/2.320 configuration write failed for an IFL ADD: File exists

-> This error is only seen when the IFL already exists in Kernel. No other case.
-> Please refer KB73443 [juniper.net] for other troubleshooting steps.