Printers discovery in Discovery Schedule vs Quick Discovery

[daware-madhu103]

Hello all,

I have encountered a problem while discovering printers in CMDB. Printers are not being discovered in the discovery schedule, whereas Quick Discovery finds and successfully discovers them.

Can anyone help me understand this issue? Is there anything different in the discovery schedule that might be causing this?

[Harish Bainsla]

No result returned from probe

In some cases a warning can be seen in the discovery log stating No result returned from probe. This is seen when an input returns empty for the OID queried by the probe. This happens because a device does not have any results to return for the specified OID, and if that is the case this is expected. If there is suspicion that discovery may be wrong, a query for the same oid against the target IP address can be run to check on the output. 

Further Documentation regarding SNMP credentials

• KB0696727: MID Server SNMP Troubleshooting

[RaghavSh]

There could be multiple reasons for this one could be the IP range you provided is does not have the printers falling in it. I believe in quick discovery you just give one target IP address.

Since you are able to find it through quick discovery it should not be the credential issue.

Also during quick you specify the mid server make sure you are using same mid server from schedule as well

[daware-madhu103]

@RaghavSh , Thank you your response.
I have checked the IP addresses and they are having IP ranges present and included under different schedules.  MID server is also same for both Quick and scheduled discovery.

[Pratiksha]

May be the prob is getting timed out. 

also check this out : https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0749673

Play with prob parameter mentioned in the post : https://noderegister.service-now.com/kb?id=kb_article_view&sysparm_article=KB0965884

I hope it will help. 

Regards,

Pratiksha

[AJ-TechTrek]

Hi @daware-madhu103 ,

Why Quick Discovery Works but Schedule Doesn’t

1. Quick Discovery runs a very direct, one-off discovery:
* It takes the IP(s) you give it.
* It probes/patterns them immediately with the selected credential(s).
* It bypasses a lot of classification/exclusion logic that a normal schedule uses.

2. Discovery Schedule has extra steps:
* MID Server selection based on IP ranges.
* IP range filters (could be excluding the printer IPs).
* Classification phase — if a device doesn’t match a supported classifier, it will be skipped before identification.
* Shun list / Discovery behavior rules could block the printer IPs.
* Credential Affinity / IP Capabilities — if the schedule can’t match the SNMP credentials to the IP, it won’t try the printer probe.

What to Check
1. Verify the IP Range in the Schedule
* Open your Discovery Schedule.
* Confirm the printer IPs are inside the range set in the schedule.
* Make sure the MID Server selected for that range can reach the printer’s IP (ping + SNMP).

2. Check the Classifiers
* Printers are discovered via SNMP (usually SNMP - Printer classifier).
* Go to Discovery → Classifiers and search for "Printer".
* Ensure your printer models are covered and the classifier conditions match (e.g., sysOID).

3. Credential Association
* In Discovery → Credentials, make sure your SNMP credential:
* Has the correct community string.
* Is associated with the correct IP ranges or is set to "All Ranges".
* Test the credential directly from the MID Server against the printer IP.

4. Check for Exclusions
* Review:
* Discovery Behavior Rules
* IP Ranges to Exclude in the schedule.
* Shun List (Discovery → Shun List) — ensure printer IPs are not there.

5. Pattern/Probe Validation
* Printers are discovered by SNMP - Printer probe.
* If you customized patterns, verify that the printer pattern is still active and not restricted.

Please appreciate the efforts of community contributors by marking appropriate response as Mark my Answer Helpful or Accept Solution this may help other community users to follow correct solution in future.
 

Thank You
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