Discover connection is not working for some devices in Spectrum

Products

• Spectrum
• Network Observability

Issue/Introduction

When trying to build topology using the discover connection, it is not working for all devices that should be connected.

Devices are enabled with CDP and LLDP protocols. 

The Discover connections functionality is enabled with the Discovery Protocol Tables set to Yes under VNM -> Information -> Modelling and Protocol Options:

And in the Discovery Console -> Modelling Configuration -> Protocol Options, all the tables that are compatible with the device are also selected:

 

Environment

DX NetOps Spectrum all currently supported releases

Cause

Searching through a MIB walk taken using Sapwalk2, there are no connections listed from the above tables. And when looking at AutoDiscovery debug, we see a lot of no connections for many of the required tables in the MIB data. For example, the following is the response in the ARP tables:

Contact lost in reading ARP table -- device myserver/0x11298d3 (SwCiscoIOS)

Contact lost in reading ARP table -- device big_switch/0x123c111 (DellEMCSwitch)

Contact lost in reading ARP table -- device switch_system/0x11e866d (SwCiscoIOS)
...
...

And then we see a lot of the following:

Device null heard 1 device(s) at MAC ....:

  Device null  heard 30 port(s) on device switch_system/0x10f543d (Sonic_Device) at MAC ....

Device null heard 1 device(s) at MAC ....

  Device null  heard 61 port(s) on device new_server/0x10f543e (Sonic_Device) at MAC ....

Device null heard 9 device(s) at MAC ....

 ...
...

The above is caused by either an issue with a 3rd party SNMP configuration tool which is blocking the MIB tables or the device agent itself not being configured to show them. 

Resolution

Unblock the following MIB tables on the device SNMP agent to allow Spectrum to discover connections:

• dot1dBridge             - 1.3.6.1.2.1.17
• dot1dTpFdbTable         - 1.3.6.1.2.1.17.4.3
• dot1dTpFdbAddress       - Neighbor Device MAC Address list -> Instance
• dot1dTpFdbPort          - Neighbor Device Port list
• dot1dTpFdbStatus        - Neighbor Port Status list
• dot1dBasePortTable      - 1.3.6.1.2.1.17.1.4
• dot1dBasePortIfIndex    - Local and Neighbor device port mapping list.
• ipAddrTable             - 1.3.6.1.2.1.4.20
• ipAdEntAddr             - 1.3.6.1.2.1.4.20.1.1
• ipAdEntIfIndex          - 1.3.6.1.2.1.4.20.1.2
• ipAdEntNetMask          - 1.3.6.1.2.1.4.20.1.3
• ipAddressAddrType       - 1.3.6.1.2.1.4.34.1.1
• ipAddressIfIndex        - 1.3.6.1.2.1.4.34.1.3
• ipCidrRouteTable        - 1.3.6.1.2.1.4.24.4
• ipCidrRouteDest         - 1.3.6.1.2.1.4.24.4.1.1 Used to find Subnet address along with ipCidrRouteMask
• ipCidrRouteNextHop      - Local Interface IP Address.
• ipCidrRouteType         - Local or Remote is only supported.
• ipCidrRouteMask         - Subnet Mask.
• ipCidrRouteIfIndex      - Local Interface Index.
• ipRouteTable            - 1.3.6.1.2.1.4.21
• ipRouteDest             - Used to find Subnet address along with ipRouteMask
• ipRouteNextHop          - Local Interface IP Address.
• ipRouteType             - Local or Remote is only supported.
• ipRouteMask             - Subnet Mask.
• ipRouteIfIndex          - Local Interface Index.
• ipNetToMediaEntry       - 1.3.6.1.2.1.4.22.1
• ipNetToMediaEntry       - 1.3.6.1.2.1.4.22.1
• ipNetToMediaIfIndex     - 1.3.6.1.2.1.4.22.1.1
• ipNetToMediaPhysAddress - 1.3.6.1.2.1.4.22.1.2
• ipNetToMediaNetAddress  - 1.3.6.1.2.1.4.22.1.3
• ipNetToMediaType        - 1.3.6.1.2.1.4.22.1.4