Quick Answer
The answer is 64 source ports per single SPAN session on most Cisco Catalyst switches. This hardware limitation exists because the switch’s switching fabric and monitoring buffer are designed to handle up to 64 ingress or egress interfaces simultaneously without degrading forwarding performance. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of SPAN session resource allocation—a common trap is confusing the 64-source-port limit with the fact that you can also monitor a single source VLAN, but you cannot mix source ports and source VLANs in the same session. Another frequent pitfall is assuming you can exceed this limit by using multiple SPAN sessions, but each session is independent and still capped at 64 sources. Remember the mnemonic “64 ports, one session—mix VLANs and ports? That’s a hard lesson.”
This 300-410 practice question tests your understanding of span, rspan, and erspan. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
What is the maximum number of source ports that can be monitored in a single SPAN session on a typical Cisco Catalyst switch?
16
Why wrong: 16 is the limit for RSPAN source sessions on some platforms, but not for local SPAN.
32
Why wrong: 32 is a common limit for the number of SPAN sessions, not source ports per session.
64
Up to 64 source ports can be included in a single SPAN session, though hardware-dependent.
128
Why wrong: 128 exceeds the typical hardware limit for source ports per session.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
64
A single SPAN session can monitor up to 64 source ports (or source VLANs, but not both in the same session). This is a hardware limitation on most Catalyst switches.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
16
Why it's wrong here
16 is the limit for RSPAN source sessions on some platforms, but not for local SPAN.
32
Why it's wrong here
32 is a common limit for the number of SPAN sessions, not source ports per session.
64
Why this is correct
Up to 64 source ports can be included in a single SPAN session, though hardware-dependent.
Related concept
Access ports place end devices into a single VLAN.
128
Why it's wrong here
128 exceeds the typical hardware limit for source ports per session.
Common exam traps
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 300-410 questions on switching, trunking, and access-port configuration.
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FAQ
SPAN, RSPAN, and ERSPAN — This question tests SPAN, RSPAN, and ERSPAN — Access ports place end devices into a single VLAN..
The correct answer is: 64 — A single SPAN session can monitor up to 64 source ports (or source VLANs, but not both in the same session). This is a hardware limitation on most Catalyst switches.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 300-410 questions on switching, trunking, and access-port configuration.
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 19, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
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