easyMultiple Choice
350-401 Practice Question: Configures SNMPv2c on a Cisco switch to send…
A network engineer configures SNMPv2c on a Cisco switch to send traps to an NMS. The engineer uses 'snmp-server community public RO' and 'snmp-server host 10.1.1.1 version 2c public'. The NMS receives traps, but the engineer notices that the traps contain the IP address of the management interface (VLAN 1) instead of the loopback interface (Loopback0) that is used for management. The engineer wants the traps to use the loopback IP as the source. What should the engineer do?
⚠ Common exam trap
Cisco often tests the exact command syntax for SNMP source interface configuration, and candidates frequently confuse 'snmp-server trap-source' with the incorrect 'snmp-server source-interface traps' or 'ip snmp source-interface'.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure 'snmp-server trap-source Loopback0'.
The correct command to set the source IP address for SNMP traps on a Cisco device is 'snmp-server trap-source Loopback0'. This command forces all SNMP trap messages to use the IP address of the specified interface as the source, regardless of which interface they exit. Option B is correct because it directly configures the trap source to the loopback interface, ensuring the NMS sees the loopback IP instead of the VLAN 1 management IP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure 'snmp-server source-interface traps Loopback0'.
Why it's wrong here
This command syntax is invalid on Cisco IOS. The 'source-interface' keyword is not used for SNMP traps; the correct command is 'snmp-server trap-source' followed by the interface name. Even if the phrase 'traps' were placed after the interface, Cisco's parser would reject it because the only global SNMP source-interface command is 'snmp-server source-interface <interface>' for all notifications, not 'traps Loopback0'. Therefore, the device would not accept this configuration, and trap source IP would remain unchanged.
- ✓
Configure 'snmp-server trap-source Loopback0'.
Why this is correct
This is the correct global configuration command for setting the source IP of SNMP traps. It instructs the router or switch to use the IP address of Loopback0 as the source address in the IP header of every trap (and inform) packet. Because a loopback interface is always reachable and never goes down, unlike a physical interface, this ensures the NMS sees a stable, predictable source IP, which is especially useful for filtering and device identification.
- ✗
Configure 'ip snmp source-interface Loopback0'.
Why it's wrong here
This command does not exist in the Cisco IOS command set. There is no 'ip snmp' global configuration mode; SNMP source-interface settings are configured under 'snmp-server' commands. The correct way to specify a trap source is 'snmp-server trap-source <interface>', which overrides the default source of the egress interface. Entering 'ip snmp source-interface Loopback0' would produce a '% Invalid input detected' error and have no effect.
- ✗
Change the management interface IP to match the loopback.
Why it's wrong here
This is not a proper solution because it would create an IP address conflict. The management interface (e.g., GigabitEthernet0/0) would need to be assigned the exact same IP as the loopback, but two interfaces on the same device cannot have identical IPv4 addresses without causing routing and ARP conflicts. Additionally, it would not solve the underlying issue: if the physical management interface goes down, the device still loses reachability, whereas a loopback remains up. The correct approach is to configure 'snmp-server trap-source Loopback0' to decouple the trap source from the egress interface's operational state.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.