My RelationshipViewer shows devices which are not real devices.
Why does the RelationshipViewer show devices which are not real devices?
The topology agent may create “Device” objects to represent unknown parts of the network topology. The “Device” objects have names of the form “Device_<IP address>_<port>” with the IP address and port of the switch that the Device connects to.
The topology agent creates the “Device” objects in the following circumstances:
- When multiple nodes are seen downstream of a switch port and none of the downstream nodes are a SNMP enabled switch, it assumes that there must be a non-SNMP enabled switch downstream of the port and creates a device to represent it. Sometimes the downstream nodes consists of virtual machines which means the port connects to the interface of a VM host.
- When multiple nodes are seen between two SNMP enabled switches, it assumes that there must be an intervening non-SNMP enabled switch between them and creates a device to represent it.
These cases may be due to one or more of the following:
- Incomplete SNMP data for the core network devices (switches and routers) in the topology.
- “Dumb” switches or hubs in the network that are not SNMP capable. These devices may not even have an IP address.
- Lack of information about VM hosts and virtual machines. This is a limitation with the current topology solution and will be improved in the future.
In the case of incomplete SNMP data, please check the following:
- All core network devices are SNMP enabled. A network administrator may need to check this and determine the correct SNMP authentication credentials for the devices.
- SNMP authentication profiles are defined to handle the core network devices.
- The core network devices are included in discovery scopes.
- The SNMP authentication profiles are mapped to the discovery scopes.
- The discovery agent has successfully discovered the core network devices via SNMP and has assigned the correct SNMP authentication profile to the device.
- The topology agent has successfully queried the device via SNMP. You may need to check the support or log files to verify this.
Often the RCA/Topology RelationshipViewer will display devices that do not look like they are part of your network. These network elements usually have a name like Device_<IP>_N, where N is some integer. In this case, the relay device is strictly a representation of a port that a group of devices are connected to. N is the port on an SNMP router or switch that this relay device represents. In theory, one router could have a relay device. This is not a common name of devices, and usually the name is based on the IP of a machine which is a real member of your network.
These machines are a synthetic inclusion into the topology. They are used to represent connective network elements that cannot be scanned by the topology_agents. There are some legitimate reasons that these elements cannot be scanned: scope restrictions, snmp credentials, non-snmp responsiveness.
If two sets of machines, defined by topology_agent scopes, can be shown to be connected, but the connecting switch or router is not included in the scopes, then the relationship_services will construct a synthetic node and add it to the list of discovered machines.
If a router, switch or similar device does not have snmp enabled, then the RCA/Topoloy services will not be able to correctly identify them. Often there are dumb hubs and relays in a network. These devices may have detectable MAC addresses, but nothing else about them can be discovered by the topology_agents. A dumb hub will not have a mac address associated with it if it is only operating on layer one. Do not expect any MAC information when viewing this device in Relationship Services. In these cases a synthetic node is generated as a place holder so that the relationship_services can make a usefully connected map.
If a switch or router is in the topology_agent scopes, but the probe has not been provided with useful snmp credentials, then the relationship_services may not construct useful relationships around this device. If the topology agent is unable to discern any relationship s with this device, it will exist as an unconnected node on the network.