All of the sudden we have Loop Protection!

[jww]

Much of our network started going down tonight and I tracked it down to an AF5X on port 2 of a WS-8-250-DC. It's on 1.4.3rc4 firmware.

The switch thought there was a loop on Port 2 and was disabling the port regularly. The relevant portion of the log is pasted below.

Our network is still flat and we don't yet use VLANs or OSPF. There is no way that I can see a loop between two ports in our network. And I definitely can't see how we'd have a loop on one port.

This configuration has been working fine for over a year and we didn't change anything tonight.

A Google search turned up a post that let me know that I could turn off Loop Protection, it's been fine since.

Any ideas? Thanks!







Jan 25 17:39:37 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 17:42:39 Loop protection: re-enabling port 2
Jan 25 17:43:38 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 17:46:40 Loop protection: re-enabling port 2
Jan 25 18:03:04 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:06:05 Loop protection: re-enabling port 2
Jan 25 18:06:39 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:09:40 Loop protection: re-enabling port 2
Jan 25 18:15:17 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:18:18 Loop protection: re-enabling port 2
Jan 25 18:22:19 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:25:21 Loop protection: re-enabling port 2
Jan 25 18:25:38 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:28:40 Loop protection: re-enabling port 2
Jan 25 18:34:13 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:37:14 Loop protection: re-enabling port 2
Jan 25 18:37:22 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:40:24 Loop protection: re-enabling port 2
Jan 25 18:41:37 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:44:39 Loop protection: re-enabling port 2
Jan 25 18:45:37 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:48:39 Loop protection: re-enabling port 2
Jan 25 18:49:33 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:52:35 Loop protection: re-enabling port 2
Jan 25 18:53:39 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds
Jan 25 18:56:41 Loop protection: re-enabling port 2
Jan 25 18:58:36 Loop protection: detected loop from port 2 to port 2, disabling port 2 for 180 seconds

[sirhc]

1) Please update your firmware.

2) Yes you can get a Loop Protection from Port 1 to Port 1

If you do a search on the forums about loop protection you get post like this one, there are many more to read through.
viewtopic.php?f=17&t=1722&p=13067&hilit=+Loop+Protection+works+same+port#p13067


search.php?keywords=%2BLoop+%2BProtection+%2Bworks+%2Bsame+%2Bport&terms=all&author=sirhc&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

[jww]

The last thing I had time to do while in the midst of a system-wide outage is to search and read through a bunch of posts. And we'll update firmware when the weather is good enough to get to the switches if something goes wrong.

Turns out the problem was that one of our customers that hosts a relay site was having problems with his Linksys WiFi router.

So he went out to our equipment enclosure and moved his cable from his routed port to a bridged port.

Something about his defective Linksys WiFi router will bring down our network when it's directly connected.

He won't do that again!

So the Netonix switch was properly doing its job. Turning off loop protection help get us mostly running again, but disconnecting the offending router made it all good again

[sirhc]

So it was a loop from one port to the same port which is what I said can happen.

Another cause of Loop Protection to detect a loop is some equipment out there has leaky VLANs which allow BPD packets to bleed across ports that should not see each other when they should NOT.

But a lot of people in the past have and still do blame us and say they have to turn Loop Protection OFF, I try to tell them we are NOT the cause and to investigate further but it falls on deaf ears.

Glad your good to go then

[jma]

All of a sudden I am having the same problem (Loop protection: detected loop on one port) with two of my MINI switches. One of the switches shuts down a port approximately every two hours. The other only did it once in the last couple of days.
They are in a flat network that has been working without problems for more than a year. We don't use VLANs or OSPF.
All the other switches (more than 20) do not have this message in the log. There is only one TP-Link switch in the complete network. All the other switches are Netonix.
I have been reading here and we have been searching and searching all over our network to find if there is a device that could be causing this.
There is nothing that we can think of unless this can be caused by a malfunctioning transmitter, router or even a bad cable?
Is there a way we can easily find what is causing this or at least on which switch we have to search? Could it be a faulty cable for example?
I suppose it can be anywhere in our network?

[sirhc]

I do not know how you do your network but if you allow customers Layer 2 access to you network if a customer creates a loop inside their network then Loop Protection will see this and take action depending on how they have their router set up as the special packet enters then exits their location and gets pack to the sending switch.


viewtopic.php?f=17&t=1459&p=12102&hilit=Loop+Protection#p12102

[jma]

Hi @sirhc. Thank you for your answer. All our clients are connected with CPE doing NAT. So I don't think a loop inside their own LAN can cause this. Or am I wrong? At the moment we only have these errors on one switch in the network. But it is approximately every two hours. I can not think of anything that could be causing this unless if this is possible because of a bad cable or unresponsive (broken?) hardware somewhere in the network.

[sirhc]

Well somehow it is getting a packet back.

I assume you are using firmware v1.4.9 ?

You can see which port is getting shut down so it has to be something on that port.

No other option you can always turn Loop protection off?

I do not think this is a switch/firmware issue or MANY people including me would be seeing it.

[jma]

Yes we are using 1.4.9.
I certainly do not believe that this is a switch/firmware issue. I was trying to find out if there is a method that I could use to locate what is causing this.
And also do not know if I have to look at devices only.
The port that is getting shut down is the port towards the rest of the network. So it can be anywhere on our complete network.

[sirhc]

OK so this port goes to another switch or router or what?

A diagram would help