SVI Not Coming Up — Interface Shows Down
Presenting Symptom
An SVI (Switch Virtual Interface) configured on a VLAN remains in down/down state even though the VLAN exists and ports are assigned.
Network Context
A small branch office with a single Cisco Catalyst 2960 switch running IOS 15.0. The switch has multiple VLANs configured, including VLAN 10 for the management network. The SVI for VLAN 10 is configured but shows as down/down. The switch has trunk links to an upstream router, and access ports in VLAN 10 are active.
Diagnostic Steps
Check SVI status
show interfaces vlan 10Vlan10 is down, line protocol is down
The SVI is down/down. This indicates either the VLAN is not active, there are no active ports in the VLAN, or the VLAN is not created in the VLAN database.
Verify VLAN exists and is active
show vlan id 10VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 10 VLAN0010 active Fa0/1, Fa0/2
If VLAN 10 is not listed or shows 'suspended' or 'inactive', the SVI will remain down. Ensure VLAN 10 is present and active.
Check if VLAN is present in VLAN database
show vlan briefVLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/3, Fa0/4, ... 10 VLAN0010 active Fa0/1, Fa0/2
If VLAN 10 is missing from the list, it was not created. If it shows 'suspended', it may be due to VTP pruning or manual suspension.
Check if VLAN is created in the running config
show running-config | include interface Vlan10interface Vlan10 ip address 192.168.10.1 255.255.255.0
If the interface Vlan10 is not present in the running config, the SVI was not configured. If it is present but the VLAN is not created, the SVI will be down.
Verify VLAN creation in global config
show running-config | include vlan 10vlan 10 name VLAN0010
If 'vlan 10' is not present, the VLAN must be created. The SVI requires the VLAN to exist in the VLAN database.
Root Cause
The SVI for VLAN 10 is down because the VLAN 10 was not created in the VLAN database. The interface Vlan10 configuration exists in the running config, but the VLAN itself is missing. An SVI requires the corresponding VLAN to be present and active in the VLAN database; otherwise, the interface remains down/down.
Resolution
Verification
Run 'show interfaces vlan 10' to confirm the SVI is up/up: Vlan10 is up, line protocol is up Hardware is EtherSVI, address is 0011.2233.4455 (bia 0011.2233.4455) Internet address is 192.168.10.1/24 Also verify with 'show vlan id 10' to confirm VLAN is active.
Prevention
1. Always create the VLAN in the VLAN database before configuring the SVI. 2. Use a consistent configuration workflow: create VLANs first, then configure SVIs. 3. Consider using a configuration template or automation to ensure VLANs and SVIs are created together.
CCNA Exam Relevance
On the CCNA 200-301 exam, this scenario appears in troubleshooting questions where an SVI is down. The exam tests the understanding that an SVI requires the VLAN to exist and be active. Candidates may be asked to identify the missing VLAN as the root cause in a multiple-choice or drag-and-drop troubleshooting scenario.
Exam Tips
Remember that an SVI will be down/down if the VLAN is not created or is suspended.
The command 'show vlan brief' is essential to verify VLAN existence and status.
Be aware that VTP can cause VLANs to be deleted or suspended; check VTP mode if VLANs disappear.
Commands Used in This Scenario
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