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jmgsoares
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Host learned on Trunk port instead of physical one

Mon Dec 04, 2023 1:05 am

Hi forum,

I've been having this issue for quite a while but never got around to fully fix it as I have a work around that kept things "working", but now I'm trying to look on how to sort this out.

I have a 2 mikrotiks and I have them connected with 2 SFP DAC cables and configured a LAG with those ports.
Then a have multiple VLANs (but for simplicity I'll be using only 2 for now) configured on both switches. Then I have a pfsense box that acts as a router.
This is a picture of a simplified setup:
Image

What happens is that PC A (on vlan 1000) will not be able to connect to the network, and this is because the CSS326-24G-2S+ switch is learning PC A mac address on the Trunk1 port instead of the actual physical port it is connected to. As a work around if I go to the switch configuration and add PC A mac address as a static host on the correct physical port everything starts to work just fine.

Any thoughts about this?

Thank you
 
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k6ccc
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Re: Host learned on Trunk port instead of physical one

Tue Dec 05, 2023 6:55 am

Never seen that one...
I don't normally have a LAG on any of my CSS326 switches, but when I have had one, the connected devices correctly showed up in the hosts table on the correct ports.
What version of SwitchOS?
 
jmgsoares
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Re: Host learned on Trunk port instead of physical one

Tue Dec 05, 2023 1:34 pm

I'm running SwOS 2.13 on both switches.

Yesterday I was messing with this a bit more and found an even more interesting thing. When I initially connect a device it is learned in the correct way. So referencing the example above, when I connect PC A on port X it will show up on the hosts table the correct info (mac address of PC A is learned on port X in vlan 1000), but after around 30 seconds or so it will change the entry from being learned on port X to Trunk1.

When I saw this I though about a quick dirty fix. I've activate port lock and lock on first in all access ports and this seems to be working so far. I'm not really comfortable with the fix tho, as I don't really know the root cause of the issue and I'm afraid this can eventually come around and cause some issues.
 
jmgsoares
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Re: Host learned on Trunk port instead of physical one

Sun Dec 10, 2023 1:58 pm

I have made some more tests and found out that this is related to the LAG feature. If I disable LAG and remove one of the links between the switches everything works normally. I can't really figure out why this happens tho.
 
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k6ccc
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Re: Host learned on Trunk port instead of physical one

Mon Dec 11, 2023 2:15 am

Let me do this in my best Rod Serling voice: Little did you know that you were living in the Twilight Zone....

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