Uplink Interface Connectivity
Configure Uplink Interface Connectivity
47
Best Practice User Guide for the Catalyst 3850 and Catalyst 3650 Switch Series
Configure an Uplink Interface to Connect to a Distribution Router (or Standalone Distribution
Switch)
Note Use this configuration when connecting the switch stack to two standalone distribution switches (not
configured as a VSS or VPC pair). However, do not use the spanning-tree portfast trunk command for
switch configuration.
• Ensure that the distribution VSS or VPC router side of the connections are configured the same and
that the EtherChannel is configured with the LACP active mode.
• For additional resilience, the configured uplink interfaces should be located on different switches in
the switch stack.
• Use the spanning-tree portfast trunk command to allow the switch side of the uplink to
immediately transition to a spanning-tree forwarding state when the link becomes available, because
routers do not participate in a spanning tree.
Figure 7 shows a switch stack having a separate EtherChannel to each distribution router. Each
EtherChannel is configured as a trunk with VLANs 10, 11, 12, 100, 200, and 999, with the native VLAN
set to 999.
interface GigabitEthernet 1/1/1
description connection to Distribution VSS or VPC switch 1
switchport mode trunk
switchport trunk native vlan 999
switchport trunk allowed vlan 10,11,12,100,200
channel-protocol lacp
channel-group 1 mode active
!
interface GigabitEthernet 2/1/1
description connection to Distribution VSS or VPC switch 1
switchport mode trunk
switchport trunk native vlan 999
switchport trunk allowed vlan 10,11,12,100,200
channel-protocol lacp
channel-group 1 mode active
!
interface GigabitEthernet 1/1/2
description connection to Distribution VSS or VPC switch 2
switchport mode trunk
switchport trunk native vlan 999
switchport trunk allowed vlan 10,11,12,100,200
channel-protocol lacp
channel-group 1 mode active
!
interface GigabitEthernet 2/1/2
description connection to Distribution VSS or VPC switch 2
switchport mode trunk
switchport trunk native vlan 999
switchport trunk allowed vlan 10,11,12,100,200
channel-protocol lacp
channel-group 1 mode active
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