When configuring MAC address table
management, go to these sections for information you are interested in:
l
Introduction
to MAC Address Table
l
Configuring
MAC Address Table Management
l
Displaying
and Maintaining MAC Address Table Management
l
MAC
Address Table Management Configuration Example
This manual covers
only static, dynamic and blackhole MAC address table management. For the management
of multicast MAC address table management, refer to Multicast Protocol
Configuration.
1.1 Introduction to MAC Address Table
A switch maintains a MAC address table for frame
forwarding. Each entry in this table contains the MAC address of a connected device,
to which port this device is connected and to which VLAN the port belongs.
A MAC address table consists of two types
of entries: static and dynamic. Static entries are manually configured and
never age out. Dynamic entries can be manually configured or dynamically
learned and may age out.
The following is how a switch learns a MAC
address after it receives a frame from a port, port A for example:
1)
Check the frame for the source MAC address (MAC-SOURCE
for example), and consider frames with destination MAC address MAC-SOURCE be
forwarded through port A.
2)
Look up the MAC address table for an entry
corresponding to the MAC address and do the following:
l
If an entry is found for the MAC address, update
the entry.
l
If no entry is found, add an entry containing
the MAC address and port A.
When receiving a frame destined for MAC A,
the switch then looks up the MAC address table and forwards it from port A.
Dynamically learned
MAC addresses cannot overwrite static MAC address entries, but the latter can
overwrite the former.
As shown in Figure 1-1, when forwarding a frame, the switch
looks up the MAC address table. If an entry is available for the destination
MAC address, the switch forwards the frame directly from the hardware. If not,
it does the following:
1)
Broadcast the frame.
2)
After the frame reaches the destination, the
destination sends back a response with its MAC address. (If no response is
received, the frame will be dropped.)
3)
Upon receipt of the response, the device adds an
entry in the MAC address table, indicating from which port the frames destined
for the MAC address should be sent.
4)
Forward subsequent frames destined for the same
MAC address directly from the hardware.
5)
Discard the frames which cannot reach the destination
MAC address.
Figure 1-1 Forward frames using the MAC
address table
1.2 Configuring MAC Address Table Management
This section covers these topics:
l
Configuring
MAC Address Entries
l
Configuring
MAC Address Aging Timer
l
Configuring
the Maximum Number of MAC Addresses an Ethernet Port or a Port Group Can Learn
1.2.1 Configuring MAC Address Entries
Follow these steps to add, modify, or
remove entries in the MAC address table:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
—
|
|
Add/modify a MAC address entry
|
mac-address blackhole mac-address vlan vlan-id
|
Required
|
|
mac-address { dynamic | static } mac-address interface
interface-type interface-number vlan vlan-id
|
|
Enter Ethernet port view
|
interface interface-type interface-number
|
—
|
|
Add/modify MAC address entries in the
specified port view
|
mac-address
{ dynamic | static } mac-address vlan
vlan-id
|
Required
|
Do not configure a
static or dynamic MAC address entry on an aggregation port.
1.2.2 Configuring MAC Address Aging Timer
The MAC address table on your device is
available with an aging mechanism for dynamic entries to prevent its resources
from being exhausted. Set the aging timer appropriately: a long aging interval
may cause the MAC address table to retain outdated entries and fail to
accommodate latest network changes; a short interval may result in removal of
valid entries and hence unnecessary broadcasts which may affect device
performance.
Follow these steps to configure the MAC
address aging timer:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
—
|
|
Configure the aging timer for dynamic MAC
address entries
|
mac-address timer { aging seconds | no-aging }
|
Optional
300 seconds by default.
|
The MAC address
aging timer takes effect globally on dynamic MAC address entries (learned or
administratively configured) only.
1.2.3 Configuring the Maximum Number of MAC Addresses an Ethernet Port or
a Port Group Can Learn
To prevent a
MAC address table from getting so large that it may degrade forwarding
performance, you may restrict the number of MAC addresses that can be learned.
One approach is to do this on a per-port or port group basis.
Follow these steps to configure the maximum
number of MAC addresses that an Ethernet port or port group can learn:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
—
|
|
Enter Ethernet port or port group view
|
Enter Ethernet port view
|
interface interface-type interface-number
|
Required
Use either command to configure on a port
or ports in a group.
|
|
Enter port group view
|
port-group { aggregation agg-id | manual port-group-name
}
|
|
Configure the maximum number of MAC
addresses that can be learned on an Ethernet port or port group.
|
mac-address max-mac-count count
|
Required
The maximum number of MAC addresses that
can be learned on a port or port group is not configured by default.
|
1.3 Displaying and Maintaining MAC Address Table Management
|
To do…
|
Use the command…
|
Remarks
|
|
Display MAC address table information
|
display mac-address blackhole [
vlan vlan-id ] [ count ]
|
Available in any view
|
|
display mac-address [ mac-address [ vlan vlan-id
] | [ dynamic | static ] [ interface interface-type
interface-number ] [ vlan vlan-id ] [ count ] ]
|
|
Display the aging timer for dynamic MAC address
entries
|
display mac-address aging-time
|
1.4 MAC Address Table Management Configuration
Example
I. Network requirements
Log onto
your device from the Console port to configure MAC address table management as
follows:
l
Set the aging timer to 500 seconds for dynamic
MAC address entries.
l
Add a static entry 000f-e235-dc71 for port GigabitEthernet
1/0/1 in VLAN 1.
II. Configuration procedure
# Add a static MAC address entry.
<Sysname> system-view
[Sysname] mac-address static 000f-e235-dc71
interface GigabitEthernet 1/0/1 vlan 1
# Set the aging timer for dynamic MAC
address entries to 500 seconds.
[Sysname] mac-address timer aging 500
# Display the MAC address entry for port GigabitEthernet
1/0/1.
[Sysname] display mac-address
interface GigabitEthernet 1/0/1
MAC ADDR VLAN ID
STATE PORT INDEX AGING TIME(s)
000f-e235-dc71 1 Config
static GigabitEthernet 1/0/1 NOAGED
--- 1 mac address(es) found
---
