Network Switch Pattern not writing to the cmdb_ci_ip_switch.serial_number field

[Matthew Glenn]

I've got an odd one here. Our Network Switch Discovery Pattern is unchanged, still in its OOB state. I believe that's worth mentioning up front. 

Now, what's happening is the Network Switch pattern is running and picking up Serial Numbers from both the chassis as well as the entPhysicalTable without issue. I witness this in the Discovery Logs, XML payloads, etc. Even when I go in and use the debug feature on the pattern itself and target a specific IP Switch, I'm able to see all the expected Serial Numbers being picked up. 

However, when I run an actual Discovery, the cmdb_serial_numbers table is populated and associated with the CI, but the cmdb_ci_ip_switch.serial_number column is not being populated. Other attributes on the record are, just not the serial number. 

I can't seem to narrow down a specific pattern for CIs that this is happening to. Certain models work as expected, others don't. 

Has anyone experienced this or have an idea on where I can start looking? I've been at it for a few hours already but can't seem to narrow down a cause.

Any help is appreciated. 

[Ashish Nahar]

If you can find the serial number in the payload and pattern log is not skipping the line which updates the CI. then i would suggest to check the reconciliation rule and see if the field is allowed to be written by servicenow discovery.

https://xxxx.service-now.com/cmdb_reconciliation_definition_list.do?sysparm_query=&sysparm_view=

If nothing works, then best way forward is to raise a case with HI Support.

Please mark correct or helpful based on impact.

[VaranAwesomenow]

Do you see anything in the discovery log for the pattern ? You can enable debugging for discovery and see that can capture it.  Do you see the related CI type added on the pattern for cmdb_ci_serial_number, I think it should be because the records are getting created, but you can check.
Also are there are BRs or scripts running on the cmdb_ci_serial_number that is affecting the IP address.

Thanks

Anil

[VaranAwesomenow]

I have just seen similar experience with models like CISCO Catalyst WS-C5500, I have reached out to hi support will let you know once I get an update.

[Matthew Glenn · Accepted solution]

This ended up being a "bug" per HI Support. This is what I received from HI and what they did to correct the issue:

What HI identified as the issue

In the network switch pattern, step "7. Insert serial number to cmdb_ci_ip_switch", is where we are inserting the serial number. 
However, in step "14. Set Switch name from DNS data if isSnmpTrusted is false", we are overriding the entire table that we are having until that point of time, to update the name of the CI. This seems to be wrong. 

And what they did to correct it

Step 14 - Set Switch name from DNS data if isSnmpTrusted is false 
We changed from table to variable since the table was erasing all the attributes in the ip_switch 

Step now looks like this

Added Step after 15 - Switch Name By DNS. 
Insert the new name without overwriting other attributes. 

New step looks like this

Hopefully this helps someone out in the future, although I'd suggest reaching out to support in the event you encounter this issue. Let them determine if this is the appropriate fix for your implementation.