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I have a VLAN dedicated for camera devices. We have learned that some camera ports keep going into the down state, and the logging indicates it is caused by STP:

sw404(config)# show logging -r 7
 Keys:   W=Warning   I=Information
         M=Major     D=Debug E=Error
----  Reverse event Log listing: Events Since Boot  ----
I 11/06/19 07:45:02 00076 ports: port 7 is now on-line
I 11/06/19 07:45:02 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:45:00 00077 ports: port 7 is now off-line
I 11/06/19 07:44:47 00076 ports: port 7 is now on-line
I 11/06/19 07:44:47 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:44:44 00077 ports: port 7 is now off-line
I 11/06/19 07:42:54 00076 ports: port 7 is now on-line
I 11/06/19 07:42:54 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:42:54 00077 ports: port 7 is now off-line
I 11/06/19 07:42:53 00076 ports: port 7 is now on-line
I 11/06/19 07:42:53 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:42:51 00077 ports: port 7 is now off-line
I 11/06/19 07:42:38 00076 ports: port 7 is now on-line
I 11/06/19 07:42:38 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:42:35 00077 ports: port 7 is now off-line
I 11/06/19 07:40:49 00076 ports: port 7 is now on-line
I 11/06/19 07:40:49 00435 ports: port 7 is Blocked by STP
I 11/06/19 07:40:47 00077 ports: port 7 is now off-line
I 11/06/19 07:40:33 00076 ports: port 7 is now on-line
I 11/06/19 07:40:33 00435 ports: port 7 is Blocked by STP

The configuration of the port should completely prevent STP from affecting the status of the port:

sw404(config)# show run int 7

Running configuration:

interface 7
   untagged vlan 2
   spanning-tree admin-edge-port
   spanning-tree bpdu-filter
   exit

Even after adding the BPDU filter and setting it for admin-edge-port, we still get errors. The cameras are not LLDP-capable and I do not get any additional information. How can I stop spanning tree from flapping the camera port(s)?

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  • 1
    Unrelated to your question but bpdufilter is very dangerous. It makes it very easy to generate a forwarding loop. Make sure to cleanse that out of your environment after troubleshooting.
    – Darrell Root
    Nov 6, 2019 at 20:50
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Dec 15, 2019 at 20:17

1 Answer 1

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How can I stop spanning tree from flapping the camera port(s)?

You did what you can already and STP isn't the problem.

I 11/06/19 07:40:33 00076 ports: port 7 is now on-line
I 11/06/19 07:40:33 00435 ports: port 7 is Blocked by STP

This state change is caused by STP - the port isn't online right away, only when STP has determined it's not causing a loop (here it is in admin-edge-port mode since it goes online right away, like portfast on Cisco).

I 11/06/19 07:40:47 00077 ports: port 7 is now off-line
I 11/06/19 07:40:33 00076 ports: port 7 is now on-line

This state change is caused by the physical link itself - faulty cable, the camera NIC, or something similar. Spanning tree never puts a port in off-line mode - loop-protect might though, if configured.

With a PoE port, it's possible that the power isn't adequate (by allocation, too long or too thin cable). 802.3af-compliant cabling (up to 13 W) must not exceed 20 ohm loop resistance, 802.3at (PoE+, up to 25 W) requires 12.5 ohm or less.

It's also possible that the cam's config causes it to restart or put the link to sleep (thx Ron!).

Try the cam with another cable or power source. Check the used cable for faults with another device.

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    I suppose it's possible that a motion-activated camera could do something like that by going to sleep and waking up.
    – Ron Maupin ♦
    Nov 6, 2019 at 18:44
  • It be the first camera that does that I'd ever heard off. This problem is quite common in IP camera installations, it's either a bad PoE injector, faulty cabling or bad camera in my experience.
    – Stuggi
    Jan 20, 2020 at 8:59

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