Basic Trunk Interface:
!
interface GigabitEthernet2/0/24
description Uplink: uplink to something special
switchport access vlan 3
switchport trunk encapsulation dot1q
switchport trunk native vlan 2
switchport trunk allowed vlan 3,50-53
switchport mode trunk
logging event trunk-status
spanning-tree cost 10
!
Where switchport trunk allowed specifies which vlans are allowed over the trunk, and spanning-tree cost 10 hard codes the cost of the link. (if you have a redundant link from a different switch, set it to 20, and it will always be the blocked link.)
Port Channel Interface:
Define the port channel interface interface Port-channel5
description Uplink: access-switch-1
switchport access vlan 2
switchport trunk encapsulation dot1q
switchport trunk native vlan 2
switchport trunk allowed vlan 249,501-503,599,753,754
switchport mode trunk
logging event trunk-status
spanning-tree cost 10
!
The vlans allowed MUST be the exact same for both. When modifying, change the interfaces before the port channel, otherwise the link will fail.
Define the uplink ports: interface GigabitEthernet1/0/17
description Uplink: access-switch-1 port g0/1
switchport access vlan 2
switchport trunk encapsulation dot1q
switchport trunk native vlan 2
switchport trunk allowed vlan 249,501-503,599,753,754
switchport mode trunk
logging event trunk-status
carrier-delay msec 0
no keepalive
channel-group 5 mode active
!
interface GigabitEthernet2/0/17
description Uplink: access-switch-1 port g0/2
switchport access vlan 2
switchport trunk encapsulation dot1q
switchport trunk native vlan 2
switchport trunk allowed vlan 249,501-503,599,753,754
switchport mode trunk
logging event trunk-status
carrier-delay msec 0
no keepalive
channel-group 5 mode active
Note that the channel-group setting can either be on or active. if you are ever having problems setting up the channel, set this to on.
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