350-401 Question #690: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An engineer configures the trunk and proceeds to configure an ESPAN session to monitor VLANs 10, 20, and 30. Which command must be added to complete this configuration?

Options

• ADevice(config-mon-erspan-src)# no filter vlan 30
• BDevice(config-mon-erspan-src-dst)# no vrf 1
• CDevice(config-mon-erspan-src-dst}# erspan-id 6
• DDevice(config-mon-erspan-src-dst)# mtu 1460

Explanation

ESPAN VLAN Filter Configuration

Option A is correct because the exhibit likely shows an ESPAN source session already filtering VLANs 10, 20, and 30, but with VLAN 30 being excluded or blocked - using no filter vlan 30 removes the exclusion of VLAN 30 from the filter, ensuring all three VLANs (10, 20, and 30) are actively monitored in the session. ESPAN filter commands operate in the config-mon-erspan-src submode, making this the appropriate context.

Option B is wrong because VRF configuration applies to routing context for the ERSPAN destination, not VLAN filtering - it has no relevance to selecting which VLANs to monitor. Option C is incorrect because erspan-id is used to match the ERSPAN flow ID between source and destination sessions, and would be configured in destination mode - it doesn't address VLAN monitoring scope. Option D is wrong because MTU adjustment affects encapsulation size for the GRE tunnel carrying ERSPAN traffic, not which VLANs are included in the monitoring session.

💡 Memory Tip: Remember that VLAN filter commands always live in the source session submode (config-mon-erspan-src), not destination mode - think "filter the source before you send it." When you need to include a VLAN that was previously excluded, use no filter vlan [x].

No community discussion yet for this question.