Load distribution methods – Allied Telesis AT-S63 User Manual
Page 104
Chapter 6: Static Port Trunks
104
Section I: Basic Operations
Load Distribution Methods
This section discusses the load distribution methods of static port trunks
and LACP port trunks, described in Chapter 7, “LACP Port Trunks” on
page 107.
When you create a static or LACP port trunk, you have to select a load
distribution method. This controls how the switch distributes the packets of
the traffic load across the ports in a trunk. The AT-S63 Management
Software has the following load distribution methods:
Source MAC Address (Layer 2)
Destination MAC Address (Layer 2)
Source MAC Address / Destination MAC Address (Layer 2)
Source IP Address (Layer 3)
Destination IP Address (Layer 3)
Source IP Address / Destination IP Address (Layer 3)
The load distribution methods examine the last three bits of a packet’s
MAC or IP address and compare the bits against mappings assigned to
the ports in the trunk. The port mapped to the matching bits is selected as
the transmission port for the packet.
In cases where you select a load distribution that employs either a source
or destination address but not both, only the last three bits of the
designated address are used in selecting a transmission port in a trunk. If
you select one of the two load distribution methods that employs both
source and destination addresses, port selection is achieved through an
XOR operation of the last three bits of both addresses.
As an example, assume you created a static or LACP aggregate trunk of
Ports 7 to 14 on a switch. The table below shows the mappings of the
switch ports to the possible values of the last three bits of a MAC or IP
address.
Assume you selected source MAC address as the load distribution
method and that the switch needed to transmit over the trunk a packet with
a source MAC address that ended in 9. The binary equivalent of 9 is 1001,
making the last three bits of the address 001. An examination of the table
above indicates that the switch would use Port 8 to transmit the frame
because that port is mapped to the matching bits.
Last 3 Bits
000
(0)
001
(1)
010
(2)
011
(3)
100
(4)
101
(5)
110
(6)
111
(7)
Trunk Ports
7
8
9
10
11
12
13
14