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By using this feature, a given flow of traffic (duplex) is ensured for the same devices
in both directions.
Symmetrical load balancing on an 802.3ad LAG utilizes a mechanism of interchanging
the source and destination addresses for a hash computation of fields, such as source
address and destination address. The result of a hash computed on these fields is
used to choose the link of the LAG. The hash-computation for the forward and reverse
flow must be identical. This is achieved by swapping source fields with destination
fields for the reverse flow. The swapped operation is referred to as complement hash
computation or
as symmetric-hash computation or
address, IP address, and port.
Configuring Symmetric Load Balancing on an 802.3ad LAG on MX Series Routers
You can specify whether symmetric hash or complement hash is done for
load-balancing traffic. To configure symmetric hash, use the
at the
symmetric hash complement, use the
option at the
These operations can also be performed at the PIC level by specifying a hash key. To
configure a hash key at the PIC level, use the
complement
hash-key family multiservice]
Consider the example in Figure 58 on page 659.
Figure 58: Symmetric Load Balancing on an 802.3ad LAG on MX Series Routers
Router A is configured with symmetric hash and Router B is configured with
symmetric hash complement. Thus, for a given flow fx, post hash computation is
from Router A to Router B through i2. The reverse traffic for the same flow fx is from
Router B to Router A through the same i2 device as its hashing (done after swapping
source and destination fields) and returns the same link index; since it is performed
on the interchanged source and destination addresses.
However, the link chosen may or may not correspond to what was attached to the
DPI. In other words, the hashing result should point to the same links that are
Configuring Symmetrical Load Balancing on an 802.3ad Link Aggregation Group on MX Series Routers
symmetric-hash complement
[edit forwarding-options hash-key family inet]
[edit forwarding-options hash-key family inet]
statement at the
[edit chassis hash-key family inet]
hierarchy levels.
i1
A
i2
i3
MX-series router
Intelligent Devices
Chapter 35: Configuring Aggregated Ethernet Interfaces
and the regular (or unswapped) operation
symmetric-hash
. The swappable fields are MAC
hierarchy level. To configure
symmetric-hash complement
hierarchy level.
symmetric-hash
B
MX-series router
A
B
Forward traffic
A
B
Reverse traffic
statement
symmetric-hash
statement and
or
symmetric-hash
and
[edit chassis
659
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