Administrator Guide
NOTE: The 802.1q Q-BRIDGE MIB defines VLANs regarding 802.1d, as 802.1d itself does not define them.
As a switchport must belong a VLAN (the default VLAN or a configured VLAN), all MAC address learned on
a switchport are associated with a VLAN. For this reason, the Q-Bridge MIB is used for MAC address query.
Moreover, specific to MAC address query, the MAC address indexes dot1dTpFdbTable only for a single
forwarding database, while dot1qTpFdbTable has two indices — VLAN ID and MAC address — to allow for
multiple forwarding databases and considering that the same MAC address is learned on multiple VLANs.
The VLAN ID is added as the first index so that MAC addresses are read by the VLAN, sorted
lexicographically. The MAC address is part of the OID instance, so in this case, lexicographic order is
according to the most significant octet.
Table 62. MIB Objects for Fetching Dynamic MAC Entries in the Forwarding Database
MIB Object OID MIB Description
dot1dTpFdbTable .1.3.6.1.2.1.17.4.3 Q-BRIDGE MIB List the learned unicast
MAC addresses on the
default VLAN.
dot1qTpFdbTable .1.3.6.1.2.1.17.7.1.2. 2 Q-BRIDGE MIB List the learned unicast
MAC addresses on non-
default VLANs.
dot3aCurAggFdb Table .1.3.6.1.4.1.6027.3.2. 1.1.5 F10-LINK-
AGGREGATION -MIB
List the learned MAC
addresses of aggregated
links (LAG).
In the following example, R1 has one dynamic MAC address, learned off of port TenGigabitEthernet 0/7,
which is a member of the default VLAN, VLAN 1. The SNMP walk returns the values for dot1dTpFdbAddress,
dot1dTpFdbPort, and dot1dTpFdbStatus.
Each object is comprised of an OID concatenated with an instance number. In the case of these objects, the
instance number is the decimal equivalent of the MAC address; derive the instance number by converting
each hex pair to its decimal equivalent. For example, the decimal equivalent of E8 is 232, and so the instance
number for MAC address 00:01:e8:06:95:ac is.0.1.232.6.149.172.
The value of dot1dTpFdbPort is the port number of the port off which the system learns the MAC address. In
this case, of TenGigabitEthernet 0/7, the manager returns the integer 118.
Example of Fetching Dynamic MAC Addresses on the Default VLAN
-----------------------------MAC Addresses on Dell Networking
System-------------------------------
Dell#show mac-address-table
VlanId Mac Address Type Interface State
1 00:01:e8:06:95:ac Dynamic Tengig 0/7 Active
----------------Query from Management Station----------------------
>snmpwalk -v 2c -c techpubs 10.11.131.162 .1.3.6.1.2.1.17.4.3.1
SNMPv2-SMI::mib-2.17.4.3.1.1.0.1.232.6.149.172 = Hex-STRING: 00 01 E8 06 95 AC
Example of Fetching Dynamic MAC Addresses on a Non-default VLANs
Simple Network Management Protocol (SNMP) 844