350-401 Automation Practice Question
A network automation team is using NETCONF to configure a Cisco IOS XE device. They send an <edit-config> RPC with the default-operation set to 'merge'. The target configuration already has an interface GigabitEthernet0/1 with an IP address of 10.1.1.1/24. The RPC payload includes a new IP address of 10.1.1.2/24 for the same interface. What will be the result on the device?
⚠ Common exam trap
The trap here is thinking that merge operation adds to existing configuration without overwriting, but for single-instance leaf nodes, it replaces the value.
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
✓
The existing IP address will be replaced with the new IP address.
The NETCONF 'merge' operation (default-operation='merge') combines the RPC's configuration with the device's existing configuration. For a leaf node such as an IP address, which can only have one value, the merge results in the new value overwriting the old one. Therefore, the interface's IP address is replaced with 10.1.1.2/24. This behavior is consistent with the NETCONF RFC 6241, where merge updates existing data and creates new data as needed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The interface will have both IP addresses configured as secondary addresses.
Why it's wrong here
NETCONF merge operation does not create secondary IP addresses automatically. In Cisco IOS XE YANG models, the IP address is a single leaf that can only hold one value. A merge operation will replace the existing value if the leaf is not a list. Secondary addresses require explicit configuration as separate list entries, which is not the case here. The merge will overwrite the existing IP.
- ✗
The device will ignore the new IP address and keep the existing one.
Why it's wrong here
NETCONF merge operation does not ignore new data; it actively merges the provided configuration into the running configuration. For a leaf node, the new value takes precedence. The device will not ignore the new IP address; it will apply it, replacing the old one. Ignoring would happen only if the operation were 'none' or if the data were invalid.
- ✓
The existing IP address will be replaced with the new IP address.
Why this is correct
In NETCONF, the 'merge' operation combines the configuration data in the RPC with the existing configuration. For a leaf node like the IP address, which is a single instance, the new value overwrites the existing value. The interface will end up with only the new IP address 10.1.1.2/24. This is because the merge operation updates the leaf with the provided value, effectively replacing the old one.
- ✗
The RPC will fail with a 'data-exists' error because the IP address is already configured.
Why it's wrong here
The 'data-exists' error occurs when using the 'create' operation on an existing node. With 'merge', the operation is designed to update existing data without error. The RPC will succeed and modify the IP address. The 'create' operation would fail if the node already exists, but 'merge' is used for updating or creating.
Go deeper
Related to this question
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SDN Controllers and Cisco ACI
Key term
NETCONF Protocol
NETCONF is a network management protocol that uses a structured data format to configure, retrieve, and modify network devices in a standard, programmatic way.
Key term
Cisco DNA Center Automation
Cisco DNA Center Automation is a centralized software platform that simplifies network management by automatically configuring, monitoring, and troubleshooting Cisco devices using policy-driven intent and software tools.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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