01-05-2023 08:57 AM - edited 01-06-2023 05:50 AM
My network consists about a 5x SG350 and 1x CBS350. They are all connected in star with leaves topology. (1->2 1->3 1-4 3->5 5->6 etc). Some are connected with LAG with 2 ports, most are just single-cable no-LAG connected. There are loops in the network.
From time to time we have a power failure somewhere as those switches have single power. Not an issue for us until a year ago.
It seems that after upgrading the SG350's that since one of the later codelevels communication can be blocked after a reboot of one of the switches. A down/up on the downlink port from the central switch always fixes the issue. But it's a very weird issue and leads to serious downtime now with each power failure.
The logs display normal link-up's and traffic-forward messages. Also CDP display normal neighbor-switch information.
I have the feeling that smartport plays a role in this, as I struggled from the same time as this issue started with Native-VLAN-mismatch errors, that appeared to be caused by auto-voiice vlan changing the isl ports from my intended VLAN configuration to a default vlan configuration.
To exclude smartport from being the cause I tried disabling smartport on one of the switches. This was a bad idea.... The switch in question was not reachable and up/down of the isl did not bring it back online. I had to fore reboot (go back to previous config) to get the switch online again. So take care when you at switch level disable smartport... Could cause you downtime!
example of the configuration on the isl port (example direct connected ports without LAG):
!
interface GigabitEthernet28
flowcontrol on
spanning-tree link-type point-to-point
switchport mode trunk
So from my perspective switch configs look good at both sides.
Any ideas? I read this post which seems to be same issue, however the solution there was to downgrade firmware. This does not really help me as it also occurs between SG350 and my new CBS350.
08-14-2024 10:05 AM
Hi, did you ever find a cause/solution for this issue, I'm running into the same thing.
08-15-2024 12:03 AM
No sadly I did not find a solution for this yet, and also no reply on the topic on this forum. Luckily we have a stable powersource so that this does not occur frequently in the environment.
08-28-2024 07:55 AM
Jpveen,
Thanks for getting back to me. I discovered the problem and solution to my issue. This problem appears to be related to the smartport feature on these switches as you suspected. I found that on reboot, this feature resets the VLAN mode on the uplink interface to Access and causes loss of connectivity to the management vlan. If you are also using a separate management vlan, you can observe this behavior by adding a management interface to your default vlan. Upon reboot, you will see your uplink port/LAG will revert to Access mode.
When you first disable the smartport feature, it will reset the VLAN mode on the interface. You will first need to add an IP to your default vlan so you can still manage it once you disable the smartport feature. I disabled the smartport feature on the uplink LAG at both ends and set it to Trunk mode. Now it no longer loses connectivity on reboot.
Let me know if you have any questions.
08-28-2024 09:19 AM
Thanks for sharing your solution.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide