Troubleshooting

How to fix Mikrotik Router freezing edge switch

For those of you who work in the enterprise environment and are using Mikrotik Routerboard products, you may have run into a case of where plugging in the Routerboard AP freezes your edge switch (lights go solid, all network traffic ceases on the switch, no one can connect, etc).  In working with a client recently, this was the case.  The client had configured the Routerboard APs for their SSID specific to their network, configured TCP/IP settings, security settings, user settings and so forth.  However, when they plugged in the routerboard AP, the switch they were using froze.  It made no difference what port the routerboard was plugged into.  Even plugging the routerboard into an untagged VLAN port seemed to hose the switch.  The switch they were using was an older HP Procurve 4208vl.

In taking a look at the routerboard a little bit closer and trying a few things, the problem turned out to be STP (Spanning Tree Protocol).  Spanning Tree Protocol’s main purpose in life is to prevent network loops.  However, as many network engineers will tell you STP can cause major nightmares in a network that is not configured correctly.  The problem with the mikrotk routerboard freezing the switch was solved by changing some configuration settings.

By using either Winbox or using the WebFig configuration page to change the following setting within the Mikrotik RouterOS.

  • Bridge >> Protocol Settings >> change to NONE
stpfeat

After the setting above was changed and the routerboard was rebooted, the switch was once again happy and traffic moved freely both from the routerboard to the switch and then from the edge switch to the core.  If you have an issue with a wireless AP and the behavior is similar to what we have described above, you culprit may not be a faulty switch but a setting such as the STP setting that is crashing the switch.  As a former boss of mine always said, “it is always in the details.”
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