Do I have a faulty Unifi US-8 switch or is it something else?

Hi everybody! I’ve been watching videos of lawrence systems for a while now and would def. would to say a massive THANK YOU because of Tom I did a very informed decision about how to set up my home network. I’ve never had an issue before… but now I have :slight_smile:

So a few days ago I upgraded a (basic) TP-Link semi-managed switch (as in: it did support VLAN’s) with a brand new Unifi US-8 switch powered over PoE for my AV needs: chromecast, receiver, bluray, IPTV box and some other stuff as well connect to this switch.

My topology is as follows:

  • pfsense connected to ‘Main Switch’ (Unifi US-8-60W, firmware v4.3.21.11325) port 1
  • ‘Main Switch’ port 6 (PoE) to ‘AV Switch’ (Unifi US-8, firmware v4.3.21.11325) port 1
  • Clients connected to ‘AV Switch’ port 2 (VLAN_IPTV) ,3 (VLAN_IOT), 4 (VLAN_IOT), 5 (VLAN_IOT), 7 (VLAN_FILTERED)

Some say an image says more than a thousand words

So, my first problem began right away: some ports did not let pass through some DHCP traffic: specifically, port 5, 6 and 7 could not get an IP from my DHCP server [1]. However, if I plugged those devices in port 2, 3 or 4, no problem at all. I did not test port 8.

However, when I started debugging that, it started working. I did not apply any change in the configuration except for enabling port 6 and 8 which I had disabled because nothing plugs in there.

A few hours later though I noticed I could not cast to the connected Chromecast, so I did take a look and surprise: that device had no link. I unplugged it, plugged it back in, nothing. I swapped ports 3 and 4 and now both links went up!

I could in fact cast some stuff but now, a few hours later I couldn’t use the Chromecast again, but this time it did have a link and was in fact connected to the network as it had an ip and I could see on screen the photos change + I could see the LED activity as well, I can even ping it without any issues as well. My best guess is that somehow UDP traffic is now being blocked by this switch?

Before all this, I never had any issue at all with the Chromecast (or the other equipment) so all these strange errors lead me to believe that maybe the switch is faulty or maybe there is a firmware issue? I did change cables but to no avail, strange errors keep appearing on this particular switch.

In the infinite wisdom of the internet, am I right to be suspicious of the switch or is there maybe something else I might have forgotten? I don’t think power is an issue, because the device consumes generally less than 5W and it is all decent quality cabling (also: cable from switch to switch is not longer than 4 [~157 inches] or 5 meters [~196 inches]).
PoE usage

It’s already a long story, but should you need more information about the setup and configuration, don’t hesitate to ask!

Greetings and thanks for taking the time to even read all this!

[1] I asked on the community forums of but did not get any answers to my initial question:

A couple of ideas.

1/ Does the US-8 come with a power brick? I’d try running it on mains supply for a bit and see if that resolves the issue

2/ Swap your old switch back in and confirm that the problems go away again. Then double check the config on the old switch and make sure you have replicated that on the new one as closely as possible.

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Hi @garethw

Thanks for your suggestion. I did put in the old switch back and as expected, I saw no errors regarding the DHCP server.

Casting did work… up until a few hours after connecting the Chromecast. So the same behavior was seen on both the old as the new switch: it appears that the issue might be elsewhere then!

Either way, I swapped the switches again and since a few days, casting began to work fine again. My guess is that some update of the Chromecast coincided with me swapping the switches.

Only yesterday I had the Chromecast disconnect from the network and it refused to create a link until I connected it to another port. If this happens again, I will try with the power brick the switch came with to see if it solved the issue, I suspecting the Chromecast however.

Apart from that, I’ve had no other issues so far, so I think my switch may not be broken after all :slight_smile:


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Sorry for the slightly late reply but that sounds like you are on the right track.