4000 Router Series Layer 2 - LAN Switching Configuration Guide

• Static entries—Static entries are manually added in order to forward frames with a specific

destination MAC address out of their associated interfaces and never age out. A static entry has

higher priority than a dynamically learned one.

• Dynamic entries—Dynamic entries can be manually configured or dynamically learned in order to

forward frames with a specific destination MAC address out of their associated interfaces and

might age out. A manually configured dynamic entry has the same priority as a dynamically

learned one.

• Blackhole entries—Blackhole entries are manually configured and never age out. Blackhole entries

are configured for filtering out frames with a specific destination MAC address. For example, to

block all frames destined for a specific user for security concerns, you can configure the MAC

address of this user as a blackhole MAC address entry.

A static or blackhole MAC address entry can overwrite a dynamic MAC address entry, but not vice

versa.

Configuring the MAC address table

The configuration tasks discussed in the following sections are all optional and can be performed in any

order.

The MAC address table can contain only Layer 2 Ethernet interfaces.

This document covers only the configuration of unicast MAC address entries, including static, dynamic,

and blackhole MAC address entries.

Configuring MAC address entries

Configuration guidelines

The manually configured static and blackhole MAC address entries cannot survive a reboot if you do not

save the configuration. The manually configured dynamic MAC address entries, however, are lost upon

reboot whether or not you save the configuration.

A frame whose source MAC address matches different types of MAC address entries is differently

processed.

Type Description

Static MAC address entry Forwards the frame.

Dynamic MAC address

entry

• Learns the MAC address of the frames entered on a different interface from

that in the entry and overwrites the original entry.

• Forwards the frame entered on the same interface with that in the entry and

updates the aging timer for the entry.

Configuration procedure

To add or modify a static or dynamic MAC address entry globally:

Step Command Remarks

1. Enter system view.

system-view N/A