This is more or less an FYI. We’ve been upgrading to N9K from NX-OS 9.3.9 to 10.4.5 and have noticed ARP entries in LibreNMS from those switches disappearing. I’ve done SNMP walks and it appears this is a Cisco problem, as ipNetToMediaIfIndex is only showing entries from default VRF. I have a TAC case open with Cisco.
Edit 03-18: Cisco TAC is still investigating and labbing up N9Ks for testing.
Like many endeavors with TAC, my case has dragged on far too long. But I have an update. This was a deliberate code change by Cisco in response to DDTS CSCvw78496 for N7K. You can see it here.
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvw78496
I am still harping on Cisco as this makes no sense with regard to SNMP at large. IP-MIB for IOS-XE and IOS-XR return ipNetToMediaPhysAddress for IPv4 and IPv6 regardless of VRF – in main/default SNMP context. And in NX-OS, IPv6 is still returned in main context. So just IPv4 information for NX-OS is stuffed into a VRF specific context. Grrr. In my opinion, if they are going to do this in SNMP, it should be across all platforms – but make it configurable. For orgs that want to provide customer access to their router’s management plane (shudder) with SNMP contexts, have at it. Stuff MIBs into contexts, etc. For those that are directly managing and monitoring a large number of VRFs, give the ability to disable the “feature”.
I’m curious how many pollers N9K can handle without failing? We have over 100 VRFs. Building out 100+ SNMP contexts is a no-go.
Last update. Cisco will not fix. It’s a “feature”.
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