How to use Layer2 Discovery to discover all the devices inside LAN?

To learn more about Layer2 Discovery, check out the video given below:

To start with, OpManager checks whether the given seed device is a Router or L3 Switch based on the below criteria, 

  1. The device must have two or more interfaces.
  2. "ipForwarding" of the device must be set to 1.

OpManager queries the OIDs in following order : CDP/LLDP OIDs, next IP routing table, next if there is any switch connection it queries the Bridge MIB and then ARP cache table. If OpManager fails to get any device connection to the seed router/L3 switch, this error message "Device Mapping not exist for this Map name" will be displayed.

List of OIDs used for Layer2 Discovery :

BRIDGE-MIB :

  • .1.3.6.1.2.1.17.4.3.1.1 
  • .1.3.6.1.2.1.17.4.3.1.2 
  • .1.3.6.1.2.1.17.4.3.1.3 
  • .1.3.6.1.2.1.17.1.4.1.1
  • .1.3.6.1.2.1.17.1.4.1.2 

RFC1213.MIB (NetToMediaTable) 

  • .1.3.6.1.2.1.4.22.1.1 
  • .1.3.6.1.2.1.4.22.1.2 
  • .1.3.6.1.2.1.4.22.1.3 
  • .1.3.6.1.2.1.4.22.1.4

RFC1213 (IPRouteTable)

  • .1.3.6.1.2.1.4.21.1.1 
  • .1.3.6.1.2.1.4.21.1.2 
  • .1.3.6.1.2.1.4.21.1.7 
  • .1.3.6.1.2.1.4.21.1.8 
  • .1.3.6.1.2.1.4.21.1.11

CISCO-CDP.MIB 

  • .1.3.6.1.4.1.9.9.23.1.2.1.1.4 
  • .1.3.6.1.4.1.9.9.23.1.2.1.1.7 
  • .1.3.6.1.4.1.9.9.23.1.2.1.1.9 

LLDP.MIB

  • .1.0.8802.1.1.2.1.4.1.1.4
  • .1.0.8802.1.1.2.1.4.1.1.5
  • .1.0.8802.1.1.2.1.4.1.1.8
  • .1.0.8802.1.1.2.1.4.1.1.9
  • .1.0.8802.1.1.2.1.4.1.1.12

IF-MIB

  • ifIndex - .1.3.6.1.2.1.2.2.1.1
  • ifName - .1.3.6.1.2.1.31.1.1.1.1

Router Discovery Algorithm:

 WebNms algorithm used:

  • "ipForwarding" of the device must be set to 1 - .1.3.6.1.2.1.4.1.0
  • Object must have two or more interfaces. - .1.3.6.1.2.1.4.20.1.1
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