# Forwarding Database (FDB)

### 1. Function Overview

The Forwarding Database (subsequently referred to as the FDB) manages the combination of destination MAC addresses, transmission ports, and VLANs.
This product uses the FDB to determine the forwarding destination port for the received frames.

1. Enable/disable acquisition function

2. Hold Time adjustment for FDB entries acquired

3. Timeout clear for FDB entries acquired

4. Manual registration of FDB entries (static entries)

### 2. Definition of Terms Used

FDB

Abbreviation of “Forwarding Data Base.”
This database manages the combination of destination MAC address, transmission port, and VLAN.

FDB entry

This is data registered in the FDB, and consists of multiple elements.

### 3. Function Details

#### 3.1. FDB entry

On this product, the contents listed in the table below are registered as a single entry in the FDB.
Up to 16,384 addresses can be registered, including addresses registered via automatic acquisition and manual registration.

Element managed | Description
--- | ---
MAC address | Device MAC addresses can be either unicast or multicast.
VLAN-ID (FID) | The VLAN ID to which the device belongs. This is a value from 1–4094.
Forwarding destination interface ID | The interface on which the device exists. LAN/SFP ports are static/LACP logical interfaces.
Action | The processing method for frames addressed to the device. There are two processing methods, “discard” and “forward”.
Entry registration type | dynamic | Entries registered through automatic acquisition
static | Entries registered manually via commands
multicast | Entries acquired by IGMP/MLD Snooping

##### 3.1.1. MAC address

This is one of the FDB key items; the VLAN-ID and MAC address are combined to become the record key.
Operation differs depending on whether the MAC address is unicast or multicast.

- Unicast
  Since the forwarding destination interface ID must be uniquely determined for a given record key, duplication is not allowed.
  (Multiple combinations of the same VLAN-ID and MAC address do not exist.)

- Multicast
  Multiple forwarding destination interface IDs may exist for a given key record.
  In this case, frames are sent to multiple forwarding destination interface IDs.

The MAC addresses of all received frames can be acquired, and the source MAC address is acquired and registered in the FDB.
However, if the transmission source MAC address is multicast, this is considered an invalid frame and is discarded without being registered.
Each VLAN interface created internally consumes one FDB entry.

Automatically acquired MAC address information is maintained until the ageing timeout.

If multiple multicast MAC addresses are specified, all are considered as one in this case.

    VLAN  port    mac             fwd      type    timeout
       1  port1.1 0100.0000.1000  forward  static       0
       1  port1.2 0100.0000.1000  forward  static       0
       1  port1.3 0100.0000.1000  forward  static       0
       1  port1.4 0100.0000.1000  forward  static       0
       1  port1.5 0100.0000.1000  forward  static       0
       1  port1.6 0100.0000.1000  forward  static       0

##### 3.1.2. VLAN-ID

MAC address acquisition is done per VLAN, and the MAC address and VLAN are managed in the FDB as a pair.
For different VLANs, identical MAC addresses are also acquired.

##### 3.1.3. Forwarding destination interface ID

The following IDs are registered.

- LAN/SFP port (port)

- Static/LACP logical interface (sa,po)

##### 3.1.4. Action

This defines the action for a received frame that matches a key record.
If the MAC address is unicast, the actions are as follows.

- forward ... Forward to the forwarding destination interface ID.

- discard ... Discard without forwarding.

If the MAC address is multicast, the actions are as follows.

- forward ... Forward to the forwarding destination interface ID.

- discard ... Cannot be specified.
  (The discard setting cannot be made if the MAC address is multicast.)

##### 3.1.5. Registration type

- dynamic …​ Registered and deleted automatically. The registration result does not remain in the config settings file.

- static …​ Registered and deleted manually, and therefore remains in the config settings file.

- multicast …​ Automatically registered and deleted by the IGMP/MLD snooping function. The registration result does not remain in the config settings file.

#### 3.2. Automatic MAC address acquisition

Automatic MAC address acquisition refers to the active creation and registration of FDB entries based on the information for the source MAC address of the received frame and the information for the reception port.
Entries registered through automatic acquisition are called “dynamic entries”.
A timer (ageing time) is used to monitor individual entries.
Entries for MAC addresses that have not received frames within a certain amount of time will be automatically deleted from FDB entries by an aging timer.
This prevents invalid device entries from being left over in the FDB due to power shutoff, being moved and so on.
If a frame is received within the specified amount of time, the monitoring timer will be reset.

The control specifications for automatic acquisition are shown below.

1. Automatic MAC address acquisition can be enabled or disabled using the mac-address-table learning command.
   The setting is enabled by default.

2. If automatic acquisition is changed from enabled to disabled, all dynamic entries that have been learned will be deleted.
   The acquisition function “disable” setting is useful when you want to flood all ports with all received frames.

3. Aging timer settings for dynamic entries are specified using mac-address-table ageing-time command.
   This value is set to 300 seconds by default.

4. The actual time when entries are deleted by the aging time occurs within double the seconds specified as the timer setting value.

5. Clear the dynamic entries that have been acquired by using the clear mac-address-table dynamic command.
   The entire contents of the FDB can be cleared at once; or a VLAN number can be specified and all MAC addresses acquired by that VLAN can be cleared from the FDB.
   Specifying the port number will clear all MAC addresses from the FDB that were acquired from that port.

6. Use the show mac-address-table command to check the automatic acquisition status.

#### 3.3. MAC address manual setting

In addition to automatic acquisition using received frames, MAC addresses can be set on this product by using user commands.
Entries that have been registered by using commands are called “static entries”.

The specifications for manual settings are shown below.

1. Use the mac-address-table static command to register static entries.

2. When registering static entries, dynamic acquisition will not be performed on the corresponding MAC addresses.
   Entries that have already been acquired will be deleted from the FDB, and will be registered as static entries.

3. Use the no mac-address-table static command to delete static entries.

4. Either “forward” or “discard” can be specified for the destination MAC address of a received frame.

   - When forwarding is specified, either the LAN/SFP port forwarding destination or the static/LACP logical interface can be specified.

   - When discarding is specified, frames received by the MAC address will not be forwarded to any port, and will be discarded.

5. If registering a multicast MAC address, you cannot specify “discard.”
   Also, the following MAC addresses cannot be registered.

   - 0000.0000.0000

   - 0100.5e00.0000～0100.5eff.ffff

   - 0180.c200.0000–0180.c200.000f

   - 0180.c200.0020–0180.c200.002f

   - 3333.0000.0000～3333.ffff.ffff

   - ffff.ffff.ffff

### 4. Related Commands

Operations | Operating commands
--- | ---
Enable/disable the MAC address learning function | mac-address-table learning
Set dynamic entry ageing time | mac-address-table ageing-time
Delete dynamic entries | clear mac-address-table dynamic
Register static entries | mac-address-table static
Delete static entries | no mac-address-table static
View the MAC address table | show mac-address-table

### 5. Examples of Command Execution

#### 5.1. Referring to the FDB

    Yamaha#show mac-address-table
    VLAN  port     mac             fwd      type     timeout
       1  port1.2  00a0.de11.2233  forward  static        0
       1  port1.1  1803.731e.8c2b  forward  dynamic     300
       1  port1.1  782b.cbcb.218d  forward  dynamic     300

#### 5.2. Delete dynamic entries

Deleting an FDB entry registered in the FDB (MAC address 00:a0:de:11:22:33)

    Yamaha#clear mac-address-table dynamic address 00a0.de11.2233

#### 5.3. Changing the dynamic entry ageing time

This example shows how to change the dynamic entry ageing time to 400 seconds.

    Yamaha(config)#mac-address-table ageing-time 400

#### 5.4. Register static entries

This example shows how frames addressed to a device associated with VLAN #10 (MAC address 00:a0:de:11:22:33) can be forwarded to LAN port 2 (port1.2).

    Yamaha(config)#mac-address-table static 00a0.de11.2233 forward port1.2 vlan 10

This example shows how to discard the frames sent to a device associated with VLAN #10 (MAC address 00:a0:de:11:22:33).
Specifying the interface name (“port1.2” in the example) will have no effect on operations. Since this cannot be omitted, specify the LAN/SFP port.

    Yamaha(config)#mac-address-table static 00a0.de11.2233 discard port1.2 vlan 10

#### 5.5. Delete static entries

This example shows how to delete the forwarding settings sent to a device associated with VLAN #10 (MAC address 00:a0:de:11:22:33).

    Yamaha(config)#no mac-address-table static 00a0.de11.2233 forward port1.2 vlan 10

### 6. Points of Caution

If the l2-unknown-mcast command is configured to discard unknown multicast frames, using the mac-address-table static command to passively forward a multicast MAC address will have no effect when registered.

### 7. Related Documentation

None

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