How does Discovery choose IP when multiple SNMP IPs exist, and is there an OID to detect management

[Satyajit Behera]

I’m working with ServiceNow Discovery for network devices using SNMP. In some subnets, the same device responds on multiple IPs (loopback, SVI VLANs, management interface, etc.). I want to understand:

1. Which IP does Discovery pick as the primary IP (cmdb_ci.ip_address) when multiple IPs are discovered?

2. Is there a way to modify the Discovery Pattern to identify and set the Management IP instead?

3. Is there a standard SNMP OID that returns the management IP?

[Fabian Kunzke]

Hello,

So to answer your question(s): the standard router & switch discovery does discover the management and/or loopback IP and sets this as the primary IP (all other IPs for the same device get set as secondary IPs). So technically speaking it should do what you want.

However, some devices might have a specialized MIB or are missing the management IP/loopback IP in the default SNMP tree. For those devices, check the manufacturers documentation. With some minor exceptions, MIBs are usually public & free. Each manufacturer could have a different SNMP tree where they store the device specific primary IP. So depending on the model & manufacturer, you may need to create an extension to the ootb discovery patterns to override the primary IP for those devices. This should be as simple as checking which device type it is and then retrieving the IP from the specific SNMP path.

Hope this helps,

regards

Fabian