The LANsurveyor map shows all nodes connected directly to a managed switch or hub with the port information adjacent to the node. In addition, LANsurveyor features a standard Switch/Hub Ports Report that provides a table of information about all nodes connected to the devices selected for the report.

Sometimes LANsurveyor cannot determine your exact network configuration from your switches and hubs. This Application Note will help you understand how LANsurveyor gathers and uses port information from managed switches and hubs so you can either adjust LANsurveyor's settings or re-examine your network configuration.

Nodes Not Connected to a Switch or Hub

Some nodes accessing the network through a switch or hub may not be shown as connected through that switch or hub on the LANsurveyor map. There are several reasons this may occur:

The correct SNMP community string was not entered.
LANsurveyor requires access to the device's management features to gather port information.

One or more switches or hubs are not managed.
A managed switch or hub supports SNMP (Simple Network Management Protocol). Without SNMP, the information required cannot be gathered from the device.

View Appendix C - SNMP Checklist of the LANsurveyor manual for more information on accessing and configuring SNMP devices.

An SNMP router or common device (server, printer, etc.) isn't included.
Switches return the table of known Ethernet addresses. Since switches know nothing about IP addresses (they operate on layer 2, not layer 3), it is essential that other nodes on the network can provide the mappings between Ethernet addresses and IP addresses.

LANsurveyor gets the information from the ARP caches of the other devices on the network using SNMP queries. Routers are ideal since the traffic from most nodes goes through routers. If a router is not available, a shared printer or server will often provide the required information.

One or more unmanaged switches or hubs are connected to a managed switch or hub.
In some office environments, users who requires more than one computer in his/her workspace purchase an inexpensive switch or hub.

In this scenario, it is impossible to determine which managed device the unmanaged device is connected to, especially when the managed device is connected to other managed devices because the Ethernet addresses for the devices connected to the unmanaged device appear in multiple switches. (The port the unmanaged device is connected to looks just like another uplink port and the connection cannot be definitive.)

You may be able to determine your actual port configuration using LANsurveyor's standard Switch/Hub Ports Report. See Physical Address below.

Switch/Hub Ports Report

The Switch/Hub Ports Report provides a list of managed switches and hubs and the port number, Ethernet address, and IP addresses for each connected device.

The Switch/Hub Ports Report includes the following information:

Switch/Hub Name: name of the switch or hub node, usually the domain name but may be the SNMP machine name (repeats for each port of the device).

IP Address: the IP address of the switch or hub (repeats for each port of the device).

Port Index: the device's internal number for indexing each port. For hubs, these will be unique across the hub. For switches, these may be repeated depending on how many Ethernet addresses have been routed through this port.

Port Description: an optional, usually more descriptive name for the port, as provided by the switch or hub.

Physical Address: the Ethernet address of the device(s) connected to this port. For hubs, there will be only one Ethernet address, which is the last Ethernet address that transmitted data on the port. For switches, there may be multiple rows in the report, each with a different Ethernet address. If a switch port is duplicated this could mean several things:

• this is an uplink or downlink port connecting switches together and the port will list some or all of the up or downstream Ethernet addresses.
• two or more devices with different Ethernet addresses have been connected to this port.
• there is an unmanaged switch or hub uplinked to the port and several nodes with different Ethernet addresses are connected to that unmanaged switch or hub.

Mapped IP Address: LANsurveyor attempts to find the IP address associated with the Ethernet address present in the Physical Address column. This column may be empty if the associated node is down or hasn't communicated via Ethernet for a long period (switch/hub configuration-dependent).

Mapped Node Name: a name associated with the IP address of the previous column, usually the domain name.

Report Information Incomplete

Some switches are set by default to flush their ethernet data relatively frequently. If your Switch/Hub Port reports are not as complete as they should be, consider running the report immediately after creating a new map or turn on the Continuous Scan option.