Multiple MACs Assigned to the Same Switch Port

Multiple MACs Assigned to the Same Switch Port

Multiple MACs Assigned to the Same Switch Port
Multiple MACs Assigned to the Same Switch Port
2024-10-15 13:40:57 - last edited 2024-10-25 00:50:07
Model: ER605 (TL-R605)  
Hardware Version: V2
Firmware Version: 2.2.6 Build 20240718 Rel.82712

Hello,

 

I have a very strange situation that I've been spending hours on.  I have a port on one of my swtiches assigned to an interface VLAN profile that has DHCP.  For some reason, that switch port is showing up in the Omada SDN device list as assigned to two different IP's as you can see in the figure.  The 192.168.50.3 IP is the one I want and has a DHCP reservation assigned for that MAC.  The other 192.168.50.100 IP is assigned to a MAC that is for the workstations BMC management port connected to a completely different switch port on a completely separate switch on a completely different VLAN and subnet.  It's not a MAC for the device plugged into that Workstation Switch Port 2.  Rebooting the switch/gateway/SDN box... nothing fixes it and I can't get to the device at 192.168.50.3.  There's no route to it when I try reaching it from another machine on the network in a different subnet (and yes, other machines are reachable in that 192.168.50 subnet from the machine I'm testing from and there are no ACL rules blocking it).  What the heck is going wrong?  Any ideas on how to fix this?  I unplugged BMC port on the workstation from the switch and the 192.168.50.100 assignment is gone (after much restarting and patiently waiting for the network h/w).  But I still can't get to the workstation on 192.168.50.3.  It's like there is no route to it even though I can get to other machines on the same subnet.  Not sure where to go from here as I'm stuck.  It's like something got hosed in the routing tables under the hood.  Thanks.

 

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#1
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Re:Multiple MACs Assigned to the Same Switch Port-Solution
2024-10-24 16:46:23 - last edited 2024-10-25 00:49:23

  @Clive_A 

 

Thanks for the reply and sorry it's been a week.  I decided to just rebuild my network and I ended up fixing the problem.  The issue was that particular server was not getting it's gateway assignment from dhcp... it was manually set.  Hence, my move of the box to a new subnet obviously caused a routing issue.  The multiple MACs assigned to the same switch port is still a mystery and not sure if it's related, but that is no longer an issue after the rebuild.

 

-D

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Re:Multiple MACs Assigned to the Same Switch Port
2024-10-15 18:15:04 - last edited 2024-10-15 18:16:19

  @celsius233 

 

do you have any of the relatively basic "easy smart" switch anywhere?  Even with careful per-port vlan assignment on them, they often sow up on my omada controller as connected to different omada switch ports and entirely incorrect VLANs than what they are actually connected to and set as.  After much diagnosing, i simply started to ignore it.  For the most part, i think that omada switch device recognition and reporting to controller is largely guesswork under the hood, and it often goes whacko.

 

I have devices on my core switch, on a defined port, that are reported by omada as connected to my Uplink LAG ports....which. of course they arent, the uplink lag ports are exactly that - uplink lag - they are just going to another switch.

 

Again, i ignore it.

 

 

When its got really confised when ive been experimenting, i often find a hard reset and reprovision fixes it until my next round of crazy fiddling.

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Re:Multiple MACs Assigned to the Same Switch Port
2024-10-15 20:03:24

  @GRL 

 

Thanks for the info.  It would really suck for me to set all this up again and that would be really unfortunate.  I have to switches in my network:   SG2008P v3.20 and SG2218P v1.20.  I would expect those to be fairly robust.  I remember seeing an "Easy..." tickbox somewhere on a Controller page, but I don't recall where right now.

 

Actually, the page wasn't false reporting.  I could get to the 192.168.50.100 landing page which was workstations BMC management port.  So it was assigning and routing to that port, i.e. it wasn't a false reporting.  I couldn't get to the 192.168.50.3 IP which was the internal NIC of the workstation.  Having removed the BMC port connection from the network, I still can't get tothe 192.168.50.3 from any subnet except the admin subnet that the gateway is on and the subnet the workstation is on.  It's like the routing is all messed up.  But I can get to other devices on the 192.168.50 subnet from all other subnets; just not the one device at 192.168.50.3.  I also tried assigning a different IP to the workstation:  192.168.50.101.  It shows up and is assigned, but again I can't get to it; even with a different assigned.  It's just stuck for that particular machine.  To make it even more strange, I plugged the second NIC in that box (different MAC) and I STILL can't get to it.  I can't see how that's possible.  It's like there is a global ACL set which is blocking the traffic, but there isn't because other devices in that subnet are reachable and I change the IP multiple times and still stuck.

 

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Re:Multiple MACs Assigned to the Same Switch Port
2024-10-16 01:59:51

Hi @celsius233 

Thanks for posting in our business forum.

Do you have a diagram and the IP config for your devices and the controller/switch settings? Screenshots of all the related for IP-MAC binding, DHCP reservation and Fixed IP if there are any on the controller/switch.

For your devices, what does the IP config look like for every one involved in this situation.

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Re:Multiple MACs Assigned to the Same Switch Port-Solution
2024-10-24 16:46:23 - last edited 2024-10-25 00:49:23

  @Clive_A 

 

Thanks for the reply and sorry it's been a week.  I decided to just rebuild my network and I ended up fixing the problem.  The issue was that particular server was not getting it's gateway assignment from dhcp... it was manually set.  Hence, my move of the box to a new subnet obviously caused a routing issue.  The multiple MACs assigned to the same switch port is still a mystery and not sure if it's related, but that is no longer an issue after the rebuild.

 

-D

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Re:Multiple MACs Assigned to the Same Switch Port
2024-10-25 08:37:27 - last edited 2024-10-25 08:38:51

  @celsius233 

 

Funnily enough - I too have had to completely rebuild my omada network from scratch including factory reset of all devices including controller.  While doing so, i discovered what, at least on my network, was causing the wrong devices to be reported as connected to the wrong ports.

 

Known Devices.

 

In my case, while i was changing interlink ports etc and using temporary links while i set port profiles on my switches, i discovered that the hardware controller, once it "learns" a device on a port, regardless if that devices changes port in the future, its somewhat "sticky" and doesn't always recognize the port change, and will continue to report the old port in the connected devices list.

 

All i had to do was go to known devices and "forget" all of them (tricky as the list repopulates as you are deleting so have to keep at it) and voila - no more port/device confusion.

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