Troubleshooting steps if the Layer 2 network map is not discovered

Troubleshooting steps if the Layer 2 network map is not discovered

If your map is not discovered after entering the details in the Discover Layer 2 Map window, or if you see the message Device mapping does not exist for this map, then follow the steps given below to troubleshoot the issue.

  • Check if the device is reachable through SNMP .
  • Verify if your seed device satisfies the following conditions: The seed device should
    1. either be a core router or an L3 switch in your network.
    2. have SNMP enabled, so that links can be fetched automatically.
    3. have ipForwarding set to 1 for the OID .1.3.6.1.2.1.4.1.0. (identified by querying the OID - 1.3.6.1.2.1.4.20.1.1)
    4. have two or more interfaces.
  • Select suitable Discovery Mechanisms from the drop-down menu.
Type of device
Discovery mechanism
Cisco device
CDP
Layer 3switches and routers
ARP
Switches
FDB
Wired LANEthernet
LLDB
Routers and switches
IP route

List of OIDs used for Layer2 Discovery

Router Discovery OIDs

OIDDescription
.1.3.6.1.2.1.4.1.0Indicates whether IP forwarding is enabled
.1.3.6.1.2.1.4.20.1.1Router interface IP address table

LLDP OIDs

OIDDescription
.1.0.8802.1.1.2.1.4.1.1.4Neighbor chassis address type (MAC/IP)
.1.0.8802.1.1.2.1.4.1.1.5Neighbor chassis address
.1.0.8802.1.1.2.1.4.1.1.8Neighbor interface name
.1.0.8802.1.1.2.1.4.1.1.9Neighbor system name
.1.0.8802.1.1.2.1.4.1.1.12System capabilities
.1.0.8802.1.1.2.1.4.2.1.2Neighbor IP address
.1.0.8802.1.1.2.1.4.2.1.3Neighbor device ifIndex

CDP OIDs

OIDDescription
.1.3.6.1.4.1.9.9.23.1.2.1.1.4Returns neighbor device IP address in hexadecimal format
.1.3.6.1.4.1.9.9.23.1.2.1.1.7Neighbor device interface name
.1.3.6.1.4.1.9.9.23.1.2.1.1.9Neighbor device type

ARP OIDs (RFC1213.MIB NetToMediaTable)

OIDDescription
.1.3.6.1.2.1.4.22.1.1Interface index
.1.3.6.1.2.1.4.22.1.2MAC address
.1.3.6.1.2.1.4.22.1.3IP address
.1.3.6.1.2.1.4.22.1.4Media type (static/dynamic)

IP Route OIDs (RFC1213 IPRouteTable)

OIDDescription
.1.3.6.1.2.1.4.21.1.1Route destination IP address
.1.3.6.1.2.1.4.21.1.2Local interface ifIndex
.1.3.6.1.2.1.4.21.1.7Next hop IP address
.1.3.6.1.2.1.4.21.1.8Route type
.1.3.6.1.2.1.4.21.1.11Route subnet mask

FDB/ Bridge MIB OIDs

OIDDescription
.1.3.6.1.2.1.17.4.3.1.1MAC address of the neighboring device
.1.3.6.1.2.1.17.4.3.1.2Port associated with the MAC address
.1.3.6.1.2.1.17.4.3.1.3Status of FDB entry
.1.3.6.1.2.1.17.1.4.1.1Bridge port number
.1.3.6.1.2.1.17.1.4.1.2ifIndex mapped to bridge port

The following tables are used to fetch interface and device details:

Interface OIDs

OIDDescription
.1.3.6.1.2.1.2.2.1.1Local device interface index
.1.3.6.1.2.1.31.1.1.1.1Local device interface name

Device Detail OIDs

OIDDescription
.1.3.6.1.2.1.1.2System Object ID (sysOID)
.1.3.6.1.2.1.1.5System Name (sysName)
.1.3.6.1.2.1.1.1System Description (sysDescription)
Notes
Router Discovery OIDs, LLDP OIDs, CDP OIDs, ARP OIDs, IP Route OIDs, and FDB OIDs are primarily used for discovering neighbor devices and building Layer 2 relationships. Additional device and interface information required for map visualization is retrieved using Interface OIDs and Device Detail OIDs.