Lab Objective
Observe the default SVI autostate behavior where an SVI's state depends on having at least one active member port, add a SPAN destination (monitoring) port to a VLAN, and configure autostate exclude on it so its inactive link status no longer affects the SVI.
Lab Purpose
An SVI, discussed earlier in this series regarding inter-VLAN routing, normally goes down when no active port remains in its VLAN. A SPAN destination port, discussed earlier in this series regarding traffic mirroring, is often intentionally left disconnected until actively needed, and by default this single inactive port can incorrectly count against the VLAN's active port total, potentially bringing down an SVI that should otherwise remain fully functional.
Lab Topology
Switch1 (Layer 3 capable, VLAN 70)
Gi1/0/5 ---- ServerA (active, VLAN 70)
Gi1/0/10 ---- SPAN destination port
(VLAN 70, currently
disconnected/unused)
SVI: interface vlan 70, 192.168.70.1/24Task 1: Configure the SVI and Verify Normal Operation
Configure interface VLAN 70 and confirm it is up while ServerA's port remains the only active member.
Task 2: Add the SPAN Destination Port to VLAN 70
Configure Gi1/0/10 as an access port in VLAN 70, intended for future SPAN monitoring use but currently disconnected.
Task 3: Observe the SVI Remains Unaffected While Other Ports Are Active
Confirm the SVI stays up, since ServerA's active port still counts.
Task 4: Simulate the Only Active Port Going Down
Shut down ServerA's port and observe the SVI going down as a result, since the disconnected SPAN port does not count as active.
Task 5: Configure Autostate Exclude and Verify SVI Stability
Restore ServerA's port, then configure autostate exclude on the SPAN destination port, and confirm the SVI's state now depends only on genuinely active data ports.
Solution and Verification
Switch1(config)# interface vlan 70
Switch1(config-if)# ip address 192.168.70.1 255.255.255.0
Switch1(config-if)# no shutdown
Switch1# show interfaces vlan 70 | include line protocol
Vlan70 is up, line protocol is upSwitch1(config)# interface gigabitethernet1/0/10
Switch1(config-if)# switchport mode access
Switch1(config-if)# switchport access vlan 70
-- Left physically disconnected, reserved
-- for future SPAN destination useSwitch1# show interfaces vlan 70 | include line protocol
Vlan70 is up, line protocol is up
-- Still up, since ServerA's port remains
-- activeSwitch1(config)# interface gigabitethernet1/0/5
Switch1(config-if)# shutdownSwitch1# show interfaces vlan 70 | include line protocol
Vlan70 is up, line protocol is down
-- The SVI went down even though the SPAN
-- destination port "exists" in VLAN 70 --
-- a disconnected, unused port does not
-- count as active, so with ServerA also
-- down, zero active ports remainSwitch1(config)# interface gigabitethernet1/0/5
Switch1(config-if)# no shutdown
Switch1# show interfaces vlan 70 | include line protocol
Vlan70 is up, line protocol is up
-- Recovered once ServerA's port came
-- back upSwitch1(config)# interface gigabitethernet1/0/10
Switch1(config-if)# switchport autostate exclude
-- This port no longer participates in the
-- SVI's up/down calculation at all,
-- regardless of its own connection statusSwitch1(config)# interface gigabitethernet1/0/5
Switch1(config-if)# shutdown
Switch1# show interfaces vlan 70 | include line protocol
Vlan70 is up, line protocol is down
-- The SVI still correctly reflects reality
-- (no genuinely active data ports remain),
-- but this demonstrates the SPAN port is
-- now excluded from the calculation entirely
-- rather than misleadingly contributing to itKey Takeaway
By default, every access port assigned to a VLAN counts toward whether that VLAN's SVI is considered up, including monitoring ports intentionally left disconnected — switchport autostate exclude removes a specific port from this calculation, ensuring the SVI's state genuinely reflects whether real data-carrying ports are active, a detail worth configuring on any dedicated SPAN destination or similarly special-purpose port.