Introduction:
My RelationshipViewer shows devices which are not real devices.
Question:
Why does the RelationshipViewer show devices which are not real devices?
Answer:
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:
These cases may be due to one or more of the following:
In the case of incomplete SNMP data, please check the following:
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.