Disabling Mac Address Learning And Limiting The Number Of Mac Addresses - Huawei AR530 series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
Figure 1-1 Aging of MAC addresses
PC1
As shown in the preceding figure, the aging time of MAC addresses is set to T. At t
with the source MAC address 00e0-fc00-0001 and VLAN ID 1 reach an interface. Assume that
the interface is added to VLAN 1. If no entry with the MAC address as 00e0-fc00-0001 and the
VLAN ID as 1 exists in the MAC address table, the MAC address is added to the MAC address
table as a dynamic MAC address entry and the flag of the matching entry is set to 1.
The switch checks all learned dynamic MAC address entries at an interval of T. For example,
at t
MAC address as 00e0-fc00-0001 and the VLAN ID as 1 is 1, the flag of the matching MAC
address entry is set to 0 and the MAC address entry is not deleted. If packets with the source
MAC address as 00e0-fc00-0001 and the VLAN ID as 1 enter the switch between t
flag of the matching MAC address entry is set to 1 again. If no packet with the source MAC
address as 00e0-fc00-0001 and the VLAN ID as 1 enters the switch between t
of the matching MAC address entry is always 0. At t
matching MAC address entry is 0, the switch assumes that the aging time of the MAC address
entry expires and deletes the MAC address entry.
As stated above, the minimum holdtime of a dynamic MAC address entry in the MAC address
table ranges from the aging time T to 2 T configured on the switch through automatic aging.
The aging time of MAC addresses is configurable. By setting the aging time of MAC addresses,
you can flexibly control the holdtime of learned dynamic MAC address entries in the MAC
address table.
1.2.2 Disabling MAC Address Learning and Limiting the Number
of MAC Addresses
The capacity of a MAC address table is limited. Therefore, when hackers forge a large quantity
of packets with different source MAC addresses and send the packets to a device, the MAC
address table of the device may reach its full capacity. When the MAC address table is full, the
device cannot learn source MAC addresses of valid packets.
A device limits the number of learned MAC addresses in one of the following modes:
Issue 01 (2014-11-30)
MAC Address
MAC3 MAC1 VLAN10
, if the switch discovers that the flag of the matching dynamic MAC address entry with the
2
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VLANID
10
MAC1
10
MAC2
MAC3
10
Swtich
Port2
Port1
Port3
Type Data
1 MAC Address Table Configuration
Port
Port1
Port2
Port3
, after discovering that the flag of the
3
PC2
PC3
, packets
1
and t , the
2 3
and t , the flag
2 3
4