Description

A pair of SNMP link up and down traps is seen on an unused ge- interface that is down and has no SFP/cable connection.

This is rare, but it can happen with ge- ports on NEO MIC[3D 20x 1GE(LAN) SFP] in MX5/10/40/80/104 platforms or MPCE/MPC2E in other MX platforms.

Symptoms

SNMP link up/down trap is reported on an unused ge- interface that is down and has no SFP/cable connection. 

User@MX> show chassis hardware

Hardware inventory:
Item             Version  Part number  Serial number     Description
FPC 1                     BUILTIN      BUILTIN           MPC BUILTIN
  MIC 0          REV 24   750-028392   xxxxxxx           3D 20x 1GE(LAN) SFP
    PIC 0                 BUILTIN      BUILTIN           10x 1GE(LAN) SFP
    PIC 1                 BUILTIN      BUILTIN           10x 1GE(LAN) SFP
Fan Tray                                                 Fan Tray

*** messages ***
Sep 19 08:50:51  MX rpd[1731]: EVENT <UpDown> ge-1/1/2 index 152 <Up Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:51  MX rpd[1733]: EVENT <UpDown> ge-1/1/2 index 152 <Up Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:51  MX rpd[1732]: EVENT <UpDown> ge-1/1/2 index 152 <Up Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:51  MX rpd[1730]: EVENT <UpDown> ge-1/1/2 index 152 <Up Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:51  MX rpd[1702]: EVENT <UpDown> ge-1/1/2 index 152 <Up Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:51  MX mib2d[1698]: SNMP_TRAP_LINK_UP: ifIndex 532, ifAdminStatus up(1), ifOperStatus up(1), ifName ge-1/1/2
Sep 19 08:50:52  MX rpd[1731]: EVENT <UpDown> ge-1/1/2 index 152 <Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:52  MX rpd[1733]: EVENT <UpDown> ge-1/1/2 index 152 <Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:52  MX rpd[1732]: EVENT <UpDown> ge-1/1/2 index 152 <Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:52  MX rpd[1730]: EVENT <UpDown> ge-1/1/2 index 152 <Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:52  MX rpd[1702]: EVENT <UpDown> ge-1/1/2 index 152 <Broadcast Multicast> address #0 40.71.83.f0.a6.8a
Sep 19 08:50:52  MX mib2d[1698]: SNMP_TRAP_LINK_DOWN: ifIndex 532, ifAdminStatus up(1), ifOperStatus down(2), ifName ge-1/1/2

User@MX > show interfaces ge-1/1/2 media
Physical interface: ge-1/1/2, Enabled, Physical link is Down
  Interface index: 152, SNMP ifIndex: 532, Generation: 155
  Description: to kopt secoundary_spare
  Link-level type: Ethernet, MTU: 1514, MRU: 1522, LAN-PHY mode, Speed: 100mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled, Auto-negotiation: Disabled, Remote fault: Online
  Pad to minimum frame size: Disabled
  Device flags   : Present Running Down
  Interface flags: Hardware-Down SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 8 supported, 8 maximum usable queues
  Hold-times     : Up 0 ms, Down 0 ms
  Damping        : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
  Current address: 40:71:83:f0:a6:8a, Hardware address: 40:71:83:f0:a6:8a
  Last flapped   : 2018-09-19 08:50:52 JST (8w6d 12:47 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  Active alarms  : LINK
  Active defects : LINK

Solution

The issue is that only this port (ex. ge-1/1/2) has link flapping occasionally, while other ports are okay.  Electrical noise can trigger this. A possibility can be noisy hardware somewhere (around ge-1/1/2) on the board.

Without the SFP plugged in, there could be noise on the input that could change the "partner ability" register for auto negotiation. If a certain short sequence of bits is received, then the "partner ability" register can be updated (/C/ character), hence the fake link up/down event.  

This link up/down snmp trap is only cosmetic, and can safely be ignored. Disabling the interface can be a workaround.

RMA is not necessary for rare occurrences, but MIC RMA is recommended for frequent occurrences.

Modification History

2018-12-18: Minor, non-technical edit.
2020-08-03: Fixed typo in the cause section.