question about turnk port configuration

[nikthatte]

We had a trunk port set up with the following config:

interface GigabitEthernet1/0/2
switchport access vlan 200
switchport mode trunk
switchport nonegotiate
no snmp trap link-status
spanning-tree portfast
end

A second admin came in and wanted to add vlan 1100 to that list so he just did "switchport trunk allowed vlan 200,1100" and we noticed there is only intermittent access to the devices on the 1100 network. Now the config looks like this:

interface GigabitEthernet1/0/2
switchport access vlan 200

switchport trunk allowed vlan 200,1100
switchport mode trunk
switchport nonegotiate
no snmp trap link-status
spanning-tree portfast
end

Every so often it will work and then traffic to and from those devices will stop. I am assuming it has something to do with the access and the trunk allowed being there at the same time. Should I just remove the access vlan line?

[Georg Pauwen]

Hello,

the 'switchport access vlan 200' has no bearing on anything, since the switchport mode is trunk. Only when you change the switchport mode to access would that line become important.

Either way, what does the rest of the network look like ? Which is the root switch for Vlans 200 and 1100 ?

[nikthatte]

both those vlans are created on that switch and are passed to vmware hosts over trunk ports connected to the hosts. vlan 200 already existed and is working correctly. Vlan 1100 was added later and is having the intermittent connectivity issue.

[Deepak Kumar · Accepted solution]

Hi,

You cant make a switch port in Access mode and Trunk mobe both at a time. You have to delete access mode command or trunk mode command from the switch. 

If you want to use this interface as a trunk than change configuration as below (Highlighted commands needs to run on both switches)

Interface GigabitEthernet1/0/2
no switchport access vlan 200

switchport trunk allowed vlan 200,1100
switchport mode trunk
switchport nonegotiate
no snmp trap link-status
no spanning-tree portfast
end

Regards,

Deepak Kumar

[nikthatte]

Thanks Deepak, that seemed to fix the issue. What does no spanning-tree portfast do?

[Deepak Kumar]

Hi,
If portfast is configured on a port and it receives a BPDU the port will disable the portfast feature. This feature is only available for the access port which will connect to end user device and will not send BPDU.
You can use Spanning-tree uplink fast feature on this port.

Sorry to say that I was mentioned a wrong command in my last post. It must me "Spanning-tree portfast disable"

Regards,
Deepak Kumar