Panasonic NN46240-502 - Manual (Page 31)

2 MAC address table configuration
Nortel Secure Router 8000 Series
Configuration - LAN Access and MAN Access
2.1 Introduction
This section describes the concepts that you need to know before you configure a MAC
address table:
• MAC address table overview
• Classification of MAC address entries
• MAC address learning limit
2.1.1 MAC address table overview
Each station or server, which is attached to a port on a router, has its own unique MAC
address. The MAC address table of a router contains the MAC addresses of all the devices
that are connected to the router.
Generally, a router automatically creates MAC address tables by learning the source addresses
of the connected devices.
Network administrators can manually bind a MAC address and a port in the table. This can
prevent malicious users with a counterfeit MAC address from logging on to the local device
through other switches.
2.1.2 Classification of MAC address entries
MAC address entries are classified into the following three types:
• Dynamic entries: Dynamic entries are learned and stored on interface boards. Dynamic
entries expire and are lost after hot swapping, interface-board resetting, or router
rebooting.
• Static entries: Users configure static entries, which are automatically delivered to each
interface board. Static entries do not expire and are not lost after hot swapping,
interface-board resetting, or router rebooting.
• Blackhole entries: Users configure blackhole entries, which are used to discard frames
containing a specified MAC address and are delivered to each interface board. Blackhole
entries do not expire and are not lost after hot swapping, or interface-board resetting, or
router rebooting.
2.1.3 MAC address learning limit
As a basic feature of Layer 2 forwarding, MAC address learning is automatically performed.
Thus, the learning process, which results in frequent attacks, is difficult to control.
By restricting the quantity of MAC addresses learned, you can control user access because the
MAC address is the basis of Layer 2 forwarding.
The MAC address learning limit controls MAC address learning by:
• setting the maximum number of MAC addresses to be learned
• controlling the speed of MAC addresses learning
• discarding or forwarding packets after the maximum number or speed of MAC address
learning is reached
• alarming network administrators after the maximum number or speed of MAC address
learning is reached
2-2 Nortel Networks Inc. Issue 5.3 (30 March 2009)