Bridge SNMP sensor

The Bridge SNMP sensor expands and updates the port data that is discovered by the SNMP MIB2 sensor (which is the data that is shown in the Ports tab of the Details pane).

The SNMP MIB2 sensor invokes the Bridge SNMP sensor. The Bridge SNMP sensor gathers the MAC address data of attached devices (specifically, the interface number through which known MAC-addressed devices can be reached), which is needed to build the Level 2 topology views.

The sensor follows the standards documented in RFC 1286 to retrieve some of the MAC Forwarding Database (fdb) table entries. The following OIDs are queried:
  • .1.3.6.1.2.1.17.4.3.1.1
  • .1.3.6.1.2.1.17.4.3.1.2
OID .1.3.6.1.2.1.17.4.3.1.1 returns a list of OIDs for known MAC addresses, as shown in the following example. These OIDs are then queried to determine the interface through which the MAC device can be accessed.
snmpwalk -v 3 -u cmdbadmin -l authPriv -a MD5 -A "" -x DES -X "" 10.189.255.1 
   .1.3.6.1.2.1.17.4.3.1.1
SNMPv2-SMI::mib-2.17.4.3.1.1.0.18.242.42.208.0 = Hex-STRING: 00 12 F2 2A D0 00
SNMPv2-SMI::mib-2.17.4.3.1.1.0.18.242.50.0.0 = Hex-STRING: 00 12 F2 32 00 00
SNMPv2-SMI::mib-2.17.4.3.1.1.0.18.242.51.88.0 = Hex-STRING: 00 12 F2 33 58 00
SNMPv2-SMI::mib-2.17.4.3.1.1.0.18.242.218.128.177 = Hex-STRING: 00 12 F2 DA 80 B1
SNMPv2-SMI::mib-2.17.4.3.1.1.0.208.4.45.228.10 = Hex-STRING: 00 D0 04 2D E4 0A

snmpwalk -v 3 -u cmdbadmin -l authPriv -a MD5 -A "" -x DES -X "" 10.189.255.1 
   .1.3.6.1.2.1.17.4.3.1.1.0.18.242.42.208.0
SNMPv2-SMI::mib-2.17.4.3.1.1.0.18.242.42.208.0 = Hex-STRING: 00 12 F2 2A D0 00

snmpwalk -v 3 -u cmdbadmin -l authPriv -a MD5 -A "" -x DES -X "" 10.189.255.1 
   .1.3.6.1.2.1.17.4.3.1.2.0.18.242.42.208.0
SNMPv2-SMI::mib-2.17.4.3.1.2.0.18.242.42.208.0 = INTEGER: 282

The Bridge SNMP sensor also provides specific details about the Computer System L2 Interfaces that are attached to the switch. The SNMP MIB2 sensor provides generic information about the existence of the device interfaces, and the Bridge SNMP sensor provides detailed information about the MAC addresses that are accessible through the device interfaces.

For example, Table 1 shows the names of MAC devices that have been discovered by the Bridge SNMP sensor. Agile Service Manager can determine the names because the computer system that owns that MAC device has been discovered. If the name of the device is unknown, the MAC address is used.

Table 1. Level 2 bridge topology data
Name Computer System L2 Interfaces
ethernet 1/9 NC84CDRS1LDPC02
ethernet 1/10 00040DFDE53
ethernet 1/11 NC84CDRS1LDPC04
ethernet 1/12 NC84CDRS1LDPC03
ethernet 10/2 000CDBF90C19
The sensor also follows the standards that are documented in RFC 1286 to retrieve some of the port table information. The following OIDs are queried:
  • .1.3.6.1.2.1.17.1.4.1.1
  • .1.3.6.1.2.1.17.1.4.1.2

Sensor name that is used in the GUI and logs

BridgeSnmpSensor

Object identifiers (OIDs) that are used

The sensor follows the standards documented in RFC 1286 to get some of the MAC Forwarding Database (fdb) table entries. The following OIDs are queried:

  • .1.3.6.1.2.1.17.4.3.1.1
  • .1.3.6.1.2.1.17.4.3.1.2

OID .1.3.6.1.2.1.17.4.3.1.1 returns a list of OIDs for known MAC addresses. These OIDs are then queried to retrieve the interface through which the MAC device can be accessed.

Model objects created

The sensor creates the following model objects:

  • net.L2Interface
  • net.Segment
  • sys.ComputerSystem