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Fetch Dynamic MAC Entries using SNMP
Dell EMC Networking supports the RFC 1493 dot1d table for the default VLAN and the dot1q table for all other VLANs.
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 111. 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 GigabitEthernet 1/21, which a member of the
default VLAN, VLAN 1. The SNMP walk returns the values for dot1dTpFdbAddress, dot1dTpFdbPort, and dot1dTpFdbStatus.
Each object comprises 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
GigabitEthernet 1/21, the manager returns the integer 118.
Example of Fetching MAC Addresses Learned on the Default VLAN Using SNMP
----------------MAC Addresses on Force10 System------------------
DellEMC#show mac-address-table
VlanId Mac Address Type Interface State
1 00:01:e8:06:95:ac Dynamic Gi 1/21 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 MAC Addresses Learned on a Non-default VLAN Using SNMP
In the following example, GigabitEthernet 1/21 is moved to VLAN 1000, a non-default VLAN. To fetch the MAC addresses
learned on non-default VLANs, use the object dot1qTpFdbTable. The instance number is the VLAN number concatenated with
the decimal conversion of the MAC address.
---------------MAC Addresses on Force10 System------------
DellEMC#show mac-address-table
VlanId Mac Address Type Interface State
1000 00:01:e8:06:95:ac Dynamic Gi 1/21 Active
---------------Query from Management Station----------------
>snmpwalk -v 2c -c techpubs 10.11.131.162 .1.3.6.1.2.1.17.7.1.2.2.1
800
Simple Network Management Protocol (SNMP)