Trunking Ports Limit

[mrogers2024]

Ladies/Gents:

Is there a trunking port limit on Cisco switches? I have a 9300L that has 4 SFP ports. Currently using 3 of the ports to trunk to other Cisco switches without issue.

Thanks,
Mark

[MHM Cisco World]

No limit at all' you can make all port in SW as trunk. 

MHM

[ToddHobbs22565]

All four of the SFP ports should allow for trunking. Are you getting any error messages? Did you check to make sure the ports aren't disabled? Is this for fiber or copper? If fiber then the SFP's need to be the same otherwise you won't get any signal.
If you run a "sh inv" command you should see all four ports displaying something similar to this:

NAME: "Gi1/1/2", DESCR: "1000BaseSX SFP"

If you don't see this output it might be the SFP you're using isn't compatible with the switch or the SFP's could possibly be mismatched.

PID: , VID: , SN: AGA1534L1KX 

[mrogers2024]

Todd:

Fiber. No error messages. Running the "sh inv" command shows the adapter description without issue. Very limited troubleshooting I can do real time. Originally, I was trying to bring up a legacy 2960 on one of the 9300Ls trunk ports. Every time I plugged in the SFP adapter on the 9300L the audio would die on both of the studios that use the other trunking ports. The other 2 SFP ports are plugged into Cisco C1000 series. I decided to buy another C1000 to replace the 2960 thinking maybe the firmware was too out of date to work with the 9300L but I get the exact same results. 

Thanks,
Mark

[MHM Cisco World]

2960 <<- check the STP mode in both SW 
you can run different mode that make trunk port down 
also do you use portfast trunk and bpduguard in C9300 port connect to 2960 ?
this issue not relate to trunk number limitation 

MHM

[ToddHobbs22565]

Has the fiber tested good?

[devrogers]

When you connect the new switch (2960 or C1000) to the 9300L, STP might be triggering a topology change, causing brief disruptions on all trunks connected to the switch. This can lead to temporary connectivity issues, which could affect sensitive traffic like audio streams.

Try:

• Ensure that Rapid PVST (Per VLAN Spanning Tree) is enabled and properly configured on all switches.

• Check the logs on the 9300L for spanning-tree events or topology changes when you plug in the new switch. Run the command:

  show spanning-tree detail | include ieee|occurr|from|is exec

  Look for messages indicating a change in the spanning-tree topology.

• Use the following command to see if any ports are going through the STP state changes:

  show spanning-tree summary

  If a topology change is detected, ensure that the 9300L is the root bridge for all VLANs, or adjust spanning-tree priorities so that it is.

[mrogers2024]

Please see attached diagram. I am just having a hard time understanding why the 9300 would behave this way when the third SFP port is plugged in. It did not behave this way when the C1000s where plugged in. 

[devrogers]

Please provide these output:

show spanning-tree detail | include ieee|occurr|from|is exec

show spanning-tree summary

[mrogers2024]

Tue Oct 01 2024 10:00:28 GMT-0500 (Central Daylight Time)
===================================================================================
#show spanning-tree detail | include ieee|occurr|from|is exec
VLAN0001 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 57 last change occurred 1w4d ago
from GigabitEthernet1/1/1

Tue Oct 01 2024 10:01:13 GMT-0500 (Central Daylight Time)
===================================================================================
#show spanning-tree summary
Switch is in rapid-pvst mode
Root bridge for: none
Extended system ID is enabled
Portfast Default is disabled
PortFast BPDU Guard Default is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default is disabled
EtherChannel misconfig guard is enabled
UplinkFast is disabled
BackboneFast is disabled
Configured Pathcost method used is long
Name Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0001 0 0 0 6 6
---------------------- -------- --------- -------- ---------- ----------
1 vlan 0 0 0 6 6

[devrogers]

I would configure the 9300L as the root bridge for all VLANs as i see it is your main switch

spanning-tree vlan 1-4094 root primary

Also enable BPDU Guard and Loop Guard on the trunk ports to prevent loops from causing network instability. 

Enable BPDU Guard and Loop Guard on the trunk ports to prevent loops from causing network instability. Use the following configuration on the 9300L’s trunk ports:

And

interface range gi1/1/1-4

spanning-tree bpduguard enable

spanning-tree guard loop

[MHM Cisco World]

Can yoh share 

Show spanning tree summary <<-for both SW

Show interface switchport <<-for both SW

MHM

[mrogers2024]

Here are the commands that are run on all switches in this network to prepare for linking to each other:

interface Gi1/0/x (x=the Ethernet port being configured)
switchport mode trunk
switchport nonegotiate
no ip igmp snooping tcn flood
end

[David Ruess]

There isn't a limit (to my knowledge) on the number of trunk ports you can configure. There would only be a limit of the amount of traffic the device can handle on the trunk if you had lower and higher BW links.

-David

[Joseph W. Doherty]

"Is there a trunking port limit on Cisco switches?"

Very possibly.  However, if there is, I would expect to be a rather large limit, i.e. unlikely you would bump into such a limit at just adding a 4th trunk port.  Also, trunk port assignments shouldn't be limited to just SFP ports, either.  That said, something like a "L" suffix model, often is feature and/of capacity limited to other models, yet, it would still seem unlikely you're limited to just 3 trunk ports.

From your follow on replies, suspect your issue has another cause.

Continue to further describe your topology and configs and what you're attempting to do and the results.