Network Management
No Topology connection with established CDP entries
This article gives information on why you may see no or only one topology connections even if the CDP data showing connection information is fully populated, both on the device and in the database.
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One of the methods that NPM determines topology is through an IP-to-IP connection utilizing CDP data for Cisco devices. This data is gathered through SNMP, specifically for these OIDS:
| cdpCacheAddressType cdpCacheAddress cdpCacheDeviceId cdpCacheDevicePort | 1.3.6.1.4.1.9.9.23.1.2.1.1.3 1.3.6.1.4.1.9.9.23.1.2.1.1.4 1.3.6.1.4.1.9.9.23.1.2.1.1.6 1.3.6.1.4.1.9.9.23.1.2.1.1.7 |
| L2 entries gathering for CISCO-CDP-MIB | |
This information will match the interface ifindex of the host device to the ifindex on the connected device, as well as provide IP-based information. This information is mapped through index value tracking, so it takes some back and forth to determine the connection. This information is then stored in the NodeCiscoCdpEntries table like this example:
These entries show that NodeID 1521 (Device 2) has four Interface connections through CDP to NodeID 1861 (Device 1). However, when you look into the TopologyConnections table, you only see the following:
One of the critical components of this data is gathering the MAC address of the interface in question, which is being used on the host device. The topology calculator looks at the ifindexes of the interfaces in question, then checks the Physical Address of the interfaces in the Interface table.
If all of the ifindexes for the CDP connections are different, then each is considered a unique connection, and the TopologyConnections table should reflect this. However, in the event that the MAC addresses are all the same, the topology calculation will take only a single entry to show a connection. This is built into the calculation to avoid showing what could be considered redundant connection information in the event of port channels or other such technology.
Unfortunately, no method exists to work around this or alter the functionality, short of changing the MAC addresses to something unique. If you want this changed, you can submit a feature request to have it included. There are also methods through database query that can manually add in the entries you want. You will need to contact SolarWinds Technical Support, and reference this article, and they should be able to direct you on how to do so and submit the feature request for you.
For more information on the Topology OIDs used by NPM, you can find them here: What object IDs (OIDs) does the Orion Platform poll for network topology information.