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[SRX] SFP-T module causes early link-up on connecting device

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Article ID: KB32252 KB Last Updated: 08 Nov 2017Version: 1.0
Summary:

This article describes the behavior of SFP-T link up during boot process on SRX300 and SRX550M series devices.

Symptoms:

The SRX300 and SRX550M series with SFP-T module cause early link-up on connecting device. This behavior is seen on following devices:

  • SRX300 
  • SRX320 
  • SRX340 
  • SRX345
  • SRX550M

Sample topology and related logs:

Topology:
SRX300(SFP-T) --(copper ethernet LAN cable)-- EX3200(ge-0/0/1)
          (192.168.30.1)                 (192.168.30.2) 

 
The following command and output shows SFP-T module is being used on SRX:
root@SRX300> show chassis hardware
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                CV3216AF0692      SRX300
Routing Engine   REV 0x08 650-065039   CV3216AF0692      RE-SRX300
FPC 0                                                    FPC
  PIC 0                                                  6xGE,2xGE SFP Base PIC
    Xcvr 6       REV 01   740-038291   F300683           SFP-T  <--- Copper SFP
         
  1. Reboot SRX300

  2. Link-down detected on EX3200 due to reboot on SRX300. 

    Oct 24 12:15:28  EX3200 rpd[1242]: EVENT <UpDown> ge-0/0/1.0 index 2147404488 <Broadcast Multicast> address #0 0.19.e2.56.e5.c4
    Oct 24 12:15:28  EX3200 rpd[1242]: EVENT UpDown ge-0/0/1.0 index 2147404472 192.168.30.2/24 -> 192.168.30.255 <Broadcast Multicast Localup>
    Oct 24 12:15:28  EX3200 rpd[1242]: EVENT <UpDown> ge-0/0/1 index 140 <Broadcast Multicast> address #0 0.19.e2.56.e5.c4

  3. Link-up detected on EX3200 in just a few seconds from SRX300 reboot. 

    Oct 24 12:15:31  EX3200 rpd[1242]: EVENT <UpDown> ge-0/0/1.0 index 2147404488 <Up Broadcast Multicast> address #0 0.19.e2.56.e5.c4
    Oct 24 12:15:31  EX3200 rpd[1242]: EVENT UpDown ge-0/0/1.0 index 2147404472 192.168.30.2/24 -> 192.168.30.255 <Up Broadcast Multicast>
    Oct 24 12:15:31  EX3200 rpd[1242]: EVENT <UpDown> ge-0/0/1 index 140 <Up Broadcast Multicast> address #0 0.19.e2.56.e5.c4

  4. Verification. On EX3200, the port status is up right after Step 3.
     
    root@EX3200> show interfaces terse ge-0/0/1
    Interface               Admin Link Proto    Local                 Remote
    ge-0/0/1                up    up
    ge-0/0/1.0              up    up   inet     192.168.30.2/24
Cause:

This behavior is by design.

Solution:

Take the following workaround to reduce possible risks considering actual network topology:

  1. Using built-in copper port

  2. Replace SFP-T module with optical module. Optical modules do not reproduce this issue.

  3. Setting "hold-time" on the connecting device. The "hold-time" configuration can suppress early link-up until SRX completes its boot process.

     
Configuration example on EX3200:

WARNING: This configuration changes default behavior.  Perform pretests to measure the impact by this setting.  Set appropriate hold-time value in accordance with actual duration time of boot process.
 
set interfaces ge-0/0/0 hold-time up 300000 (300000 milliseconds is equal to 5 minutes.)
set interfaces ge-0/0/0 hold-time down 0
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