Trunk Port Suggestions

[adam.dillon1]

I currently have one branch of my network connected via copper lines, we are in the process of putting fiber to these switches, and I'd like to get the fiber up and tested while the copper is in place.

The connection I have now is from a 3750 to a 2960 This is the configuration:

Copper 3750 to 2960

3750 GI4/0/1:

interface GigabitEthernet4/0/1
  switchport trunk encapsulation dot1q
 switchport mode trunk
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
end

2960 gi1/0/24:

interface GigabitEthernet1/0/24
 switchport mode trunk
 speed auto 10 100
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
end

This is what my Fiber trunk port looks like.

3750:

interface GigabitEthernet1/0/27
 switchport mode trunk
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
end

2960:

interface GigabitEthernet1/0/27
 switchport mode trunk
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
end

I'm worried about causing a loop. Can anybody tell me if I'll get a loop from this configuration and provide suggestions?

[Reza Sharifi · Accepted solution]

As long as spanning tree is not turned off and configured correctly, after connecting the fiber link one of them will go into blocking mode. That said, I would still make the change during none business hours just in case there is any issue.

HTH

[adam.dillon1]

Is spanning tree configured per port?

If so, it doesn't look like I have it configured.

I found this in the config as well

spanning-tree mode pvst
spanning-tree extend system-id

After doing some research it appeared that is what I needed. I switched the fiber over and the copper went into block.

Thanks.