© Copyright Lenovo 2017
193
Chapter 11. Virtual Link Aggregation Groups
In
many
data
center
environments,
downstream
servers
or
switches
connect
to
upstream
devices
which
consolidate
traffic.
For
example,
see
.
Figure 16.
Typical
Data
Center
Switching
Layers
with
STP
vs.
VLAG
As
shown
in
the
example,
a
switch
in
the
access
layer
may
be
connected
to
more
than
one
switch
in
the
aggregation
layer
to
provide
for
network
redundancy.
Typically,
Spanning
Tree
Protocol
(RSTP,
PVRST,
or
MSTP—see
)
is
used
to
prevent
broadcast
loops,
blocking
redundant
uplink
paths.
This
has
the
unwanted
consequence
of
reducing
the
available
bandwidth
between
the
layers
by
as
much
as
50%.
In
addition,
STP
may
be
slow
to
resolve
topology
changes
that
occur
during
a
link
failure,
and
can
result
in
considerable
MAC
address
flooding.
Using
Virtual
Link
Aggregation
Groups
(VLAGs),
the
redundant
uplinks
remain
active,
utilizing
all
available
bandwidth.
Two
switches
are
paired
into
VLAG
peers,
and
act
as
a
single
virtual
entity
for
the
purpose
of
establishing
a
multi
‐
port
aggregation.
Ports
from
both
peers
can
be
grouped
into
a
VLAG
and
connected
to
the
same
LAG
‐
capable
target
device.
From
the
perspective
of
the
target
device,
the
ports
connected
to
the
VLAG
peers
appear
to
be
a
single
LAG
connecting
to
a
single
logical
device.
The
target
device
uses
the
configured
Tier
ID
to
identify
the
VLAG
peers
as
this
single
logical
device.
It
is
important
that
you
use
a
unique
Tier
ID
for
each
VLAG
pair
you
configure.
The
VLAG
‐
capable
switches
synchronize
their
logical
view
of
the
access
layer
port
structure
and
internally
prevent
implicit
loops.
The
VLAG
topology
also
responds
more
quickly
to
link
failure
and
does
not
result
in
unnecessary
MAC
flooding.
VLAGs
are
also
useful
in
multi
‐
layer
environments
for
both
uplink
and
downlink
redundancy
to
any
regular
LAG
‐
capable
device.
For
example:
STP blocks
implicit loops
Links remain
active
Access
Layer
Servers
Aggregation
Layer
VLAG
Peers
VLAGs
ISL
Summary of Contents for Flex System Fabric CN4093
Page 27: ... Copyright Lenovo 2017 27 Part 1 Getting Started ...
Page 28: ...28 CN4093 Application Guide for N OS 8 4 ...
Page 58: ...58 CN4093 Application Guide for N OS 8 4 ...
Page 72: ...72 CN4093 Application Guide for N OS 8 4 ...
Page 85: ... Copyright Lenovo 2017 85 Part 2 Securing the Switch ...
Page 86: ...86 CN4093 Application Guide for N OS 8 4 ...
Page 98: ...98 CN4093 Application Guide for N OS 8 4 ...
Page 112: ...112 CN4093 Application Guide for N OS 8 4 ...
Page 136: ...136 CN4093 Application Guide for N OS 8 4 ...
Page 156: ...156 CN4093 Application Guide for N OS 8 4 ...
Page 192: ...192 CN4093 Application Guide for N OS 8 4 ...
Page 228: ...228 CN4093 Application Guide for N OS 8 4 ...
Page 229: ... Copyright Lenovo 2017 229 Part 4 Advanced Switching Features ...
Page 230: ...230 CN4093 Application Guide for N OS 8 4 ...
Page 298: ...298 CN4093 Application Guide for N OS 8 4 ...
Page 382: ...382 CN4093 Application Guide for N OS 8 4 ...
Page 392: ...392 CN4093 Application Guide for N OS 8 4 ...
Page 416: ...416 CN4093 Application Guide for N OS 8 4 ...
Page 452: ...452 CN4093 Application Guide for N OS 8 4 ...
Page 466: ...466 CN4093 Application Guide for N OS 8 4 ...
Page 496: ...496 CN4093 Application Guide for N OS 8 4 ...
Page 508: ...508 CN4093 Application Guide for N OS 8 4 ...
Page 510: ...510 CN4093 Application Guide for N OS 8 4 ...
Page 514: ...514 CN4093 Application Guide for N OS 8 4 ...
Page 538: ...538 CN4093 Application Guide for N OS 8 4 ...
Page 539: ... Copyright Lenovo 2017 539 Part 7 Network Management ...
Page 540: ...540 CN4093 Application Guide for N OS 8 4 ...
Page 554: ...554 CN4093 Application Guide for N OS 8 4 ...
Page 576: ...576 CN4093 Application Guide for N OS 8 4 ...
Page 596: ...596 CN4093 Application Guide for N OS 8 4 ...
Page 604: ...604 CN4093 Application Guide for N OS 8 4 ...
Page 609: ... Copyright Lenovo 2017 609 Part 9 Appendices ...
Page 610: ...610 CN4093 Application Guide for N OS 8 4 ...
Page 626: ...626 CN4093 Application Guide for N OS 8 4 ...
Page 633: ......
Page 634: ...Part Number 00MY375 Printed in USA IP P N 00MY375 ...