2 Replies Latest reply on May 6, 2016 9:55 AM by nkillgore

    UDT not working on Nexus FEX units

    automag928

      I've run into an issue with UDT polling Nexus FEX ports.  Basic background - the majority of my network over the last few years has migrated from Cat6500s to Nexus 7018s, with FEX 2248s.  I've had users come to me and tell me they aren't seeing MACs and IPs for devices on the Nexus switches.  I started doing some exploring and also opened a case with SW support (822548) and here's what I've found -

       

      Using the UDT compatibility checker on a Nexus, I'm noticing the vmMembershipSummaryTable is not being populated by the switch for layer 2 access ports on the FEX.  It does populate if there is a line card port assigned to a vlan on the Nexus. For example, switch Nexus1 has a 10/100/1000 Ethernet Module in slot 1, and on port 48 its in vlan 10, the vmMembershipSummaryTable populates for vlan 10.  However, if vlan 10 ports are ONLY on the FEX unit, i.e. Ethernet101/1/48 is a switch port assigned to vlan10, it will not populate the vmMembershipSummaryTable.  The problem with my network of Nexus is I don't have many line cards with layer 2 access ports, most are 10 gig modules with trunks connected to multiple FEX units which have all the layer 2 ports.

       

      I've opened a case with Cisco on this after my case with solar winds, and Cisco says basically nothing is broken.  The port ifindex for the FEX ports is greater than 2048, which prevents the vmMembershipSummaryTable from populating.  Because this table isn't populating, SW doesn't know which vlans to go in and grab the dot1dBasePortTable@vlanXXX - thus applying the mac address to the switch port.

       

      Just curious if anyone else has run into this issue and if so if there was any work around to get Nexus FEX units reporting mac/ip in UDT.