Hi Johan,

The error you’re encountering suggests that the NetBox API requires both terminations (termination_a and termination_b) to be properly defined when creating a cable. Based on the code you’ve shared, the issue may be with the naming of the parameters or the exact structure of the create() function.

In NetBox v4.x, the parameters for creating a cable have slightly changed. The terminations need to be specified as a list of dictionaries. Here’s an updated version of your code that should work:

Updated Code:
python
Kodu kopyala
import pynetbox

Initialize the NetBox API

nb = pynetbox.api('http://10.129.201.216/', token='all long code')

Define the terminations

termination_a = {
"object_type": "dcim.interface",
"object_id": 1326 # Ethernet 11 on evs-edge-1
}
termination_b = {
"object_type": "dcim.interface",
"object_id": 1350 # Ethernet 1 on evs-spine-1
}

try:
# Create the new cable
new_cable = nb.dcim.cables.create(
terminations=[termination_a, termination_b]
)
print(f"Cable created successfully: {new_cable}")
except pynetbox.RequestError as e:
# Handle the request error
print(f"The request failed with code {e.response.status_code}: {e.error}")
Key Changes:
terminations Field: In NetBox v4.x, terminations are provided as a list of dictionaries with object_type and object_id keys.
Correct Parameter Names: Updated the structure to match the current API documentation.
Additional Notes:
Ensure your API token has sufficient permissions to create cables.
Verify that the object_type values (dcim.interface) are correct. These should match the type in your NetBox installation.
If the issue persists, you can use a tool like curl or Postman to manually test the API endpoint and ensure it’s functioning as expected.
Let me know if this resolves your issue or if you need further assistance.

Best regards

Hi,
Thanks for your answer but unfortunately it gives the same error.
I checked the values and apparently all are existing.
So if you have more hints, please let me know.
Kind regards
Johan

This is most likely related to API changes introduced in newer NetBox 4.x versions.

Older examples using:

termination_a_type
termination_a_id
termination_b_type
termination_b_id

do not work correctly anymore for cable creation.

Also, using:

terminations=[...]

still throws the same validation error on some newer NetBox releases because the API now expects explicit A/B termination groups.

Try using:

new_cable = nb.dcim.cables.create(
    a_terminations=[
        {
            "object_type": "dcim.interface",
            "object_id": 1326
        }
    ],
    b_terminations=[
        {
            "object_type": "dcim.interface",
            "object_id": 1350
        }
    ],
    status="connected"
)

The important part is using:

a_terminations
b_terminations

instead of the older single terminations structure.

I hit something similar recently when working with NetBox 4.x + newer pynetbox versions, and the older examples from previous documentation/posts were still showing up in search results.

Since your interfaces already exist and connectivity works from DataGrip, the issue is probably not authentication or networking but simply the payload structure expected by the newer API version.

The original code uses:

termination_a_type
termination_a_id
termination_b_type
termination_b_id

That structure worked in older NetBox versions but no longer works properly in newer NetBox 4.x releases.

Another incorrect suggestion in the thread is:

terminations=[termination_a, termination_b]

Even though it looks valid, newer NetBox versions often still reject it with:

Must define A and B terminations when creating a new cable.

because the API now expects explicit separation between side A and side B terminations.

The correct fix is to use:

a_terminations
b_terminations

with list objects.

Correct working example:

import pynetbox

nb = pynetbox.api(
'http://10.129.201.216/',
token='all long code'
)

new_cable = nb.dcim.cables.create(
a_terminations=[
{
"object_type": "dcim.interface",
"object_id": 1326
}
],
b_terminations=[
{
"object_type": "dcim.interface",
"object_id": 1350
}
],
status="connected"
)

print(new_cable)

Why this fixes it:

NetBox 4.x changed the cable creation payload format
The API now validates explicit A-side and B-side termination groups
Older payload styles are still found online and in old examples, which causes confusion