A Switch CI is created for Cisco Fabric Extender (FEX) units, as if it were a Stacked Switch - Known Error

A Switch CI is created for Cisco Fabric Extender (FEX) units, as if it were a Stacked Switch Description The Network Switch pattern and Stacked Switch pattern library is confused by some Cisco "Nexus" switches and will create a secondary stacked switch CI for a Cisco Nexus 2000 series Fabric Extender (FEX) unit. The pattern is designed to treat FEX units as additional ports of the main switch CI, but we assume if OID 1.3.6.1.2.1.47.1.1.1.1 is populated then it must be a stacked switch, which is populated in older switches such as N5K-C5548UP.

Note: Cisco "Catalyst" is a stacked switch architecture, but "Nexus + FEX" is not. CIs are not expected to be created for FEX units, and there is no out-of-box CI class for FEX . See this KB for more information: KB0830746 Are Cisco Fabric Extender (FEX) devices supported by Discovery

Steps to Reproduce

Install the Discovery plugin, set up a MID Server, and provide SNMP credentials Discover a Cisco Nexus N5K-C5548UP switch, that has a 2000 series FEX attached Expected behaviour: The FEX will be visible only as additional ports/interfaces on the single Nexus switch CI

Actual behaviour: An additional switch class CI, in addition to the main switch CI, is created for the FEX (and will have things wrong with its attributes, such as the same Model name/Serial of the main switch unit)

Workaround The fix has been targeted for SR - ITOM - ITOM Visibility Content 202211 release (the last week of November) and it will disable Stacked Switches shared library for Cisco Nexus devices only because Nexus devices do not support stacking. Network Switch pattern will stop creating seconday / slave IP switch records for FEX.

Cisco Nexus pattern development is in the R&D queue which means Network Switch pattern doesn't support FEX discovery at the moment.

https://docs.servicenow.com/bundle/tokyo-it-operations-management/page/product/service-mapping/reference/r_SupportedApplications.html

However CMDB will require a cleanup and FEX IP Switches will have to be deleted:

If you run the fix script as it is it will print all FEX secondary / slave switches. If you replace read_only by delete and you uncomment setWorkflow and deleteRecord statements the script will delete them. //Set the mode: "read_only" mode for only printing the wrong records. Set "delete" mode to print the wrong records and delete them as well. var mode="read_only"; function truncateString(string, limit) { if (string.length > limit) { return string.substring(0, limit) + "..." } else { return string } } var count = 0; var device = new GlideRecord("cmdb_ci_ip_switch"); device.addQuery('stack', true); device.addQuery('short_description', 'CONTAINS', 'Cisco NX-OS'); device.addQuery('stack_mode', 'Slave'); device.query(); while(device.next()) { var short_description = device.getValue('short_description'); var desc = truncateString(short_description, 50); count++; if(mode == "delete"){ gs.log("DELETING " + "name: [" +device.name + "] sys_id: [" + device.sys_id + "]\n" + " ip_address: [" + device.ip_address + "]\n" + " serial: [" + device.serial_number + "]\n" + " stack: [" + device.stack + "]" + " stack_mode: [" + device.stack_mode + "]\n" + " description: [" + desc + "]"); // device.setWorkflow(false); // device.deleteRecord(); } else { gs.log("PLAN DELETING " + "name: [" +device.name + "] sys_id: [" + device.sys_id + "]\n" + " ip_address: [" + device.ip_address + "]\n" + " serial: [" + device.serial_number + "]\n" + " stack: [" + device.stack + "]\n" + " stack_mode: [" + device.stack_mode + "]\n" + " description: [" + desc + "]"); } } gs.log('================================================') if(mode == "delete"){ gs.log('# of Nexus Slaves deleted: ' + count); } else { gs.log('# of Nexus Slaves to be deleted: ' + count); } If you have any additional question be free to contact ServiceNow Technical Support or subscribe to this Known Error article by clicking the Subscribe button at the top right of this article to be notified when more information becomes available.