<s>
EtherChannel	B-Protocol
is	O
a	O
port	O
link	B-Architecture
aggregation	I-Architecture
technology	O
or	O
port-channel	O
architecture	O
used	O
primarily	O
on	O
Cisco	O
switches	B-Protocol
.	O
</s>
<s>
It	O
allows	O
grouping	O
of	O
several	O
physical	O
Ethernet	O
links	O
to	O
create	O
one	O
logical	O
Ethernet	O
link	O
for	O
the	O
purpose	O
of	O
providing	O
fault-tolerance	O
and	O
high-speed	O
links	O
between	O
switches	B-Protocol
,	O
routers	O
and	O
servers	O
.	O
</s>
<s>
An	O
EtherChannel	B-Protocol
can	O
be	O
created	O
from	O
between	O
two	O
and	O
eight	O
active	O
Fast	O
,	O
Gigabit	O
or	O
10-Gigabit	O
Ethernet	O
ports	B-Protocol
,	O
with	O
an	O
additional	O
one	O
to	O
eight	O
inactive	O
(	O
failover	B-General_Concept
)	O
ports	B-Protocol
which	O
become	O
active	O
as	O
the	O
other	O
active	O
ports	B-Protocol
fail	O
.	O
</s>
<s>
EtherChannel	B-Protocol
is	O
primarily	O
used	O
in	O
the	O
backbone	B-General_Concept
network	I-General_Concept
,	O
but	O
can	O
also	O
be	O
used	O
to	O
connect	O
end	O
user	O
machines	O
.	O
</s>
<s>
EtherChannel	B-Protocol
technology	O
was	O
invented	O
by	O
Kalpana	O
in	O
the	O
early	O
1990s	O
.	O
</s>
<s>
In	O
2000	O
,	O
the	O
IEEE	O
passed	O
802.3ad	B-Architecture
,	O
which	O
is	O
an	O
open	O
standard	O
version	O
of	O
EtherChannel	B-Protocol
.	O
</s>
<s>
Using	O
an	O
EtherChannel	B-Protocol
has	O
numerous	O
advantages	O
,	O
and	O
probably	O
the	O
most	O
desirable	O
aspect	O
is	O
the	O
bandwidth	O
.	O
</s>
<s>
Using	O
the	O
maximum	O
of	O
8	O
active	O
ports	B-Protocol
a	O
total	O
bandwidth	O
of	O
800	O
Mbit/s	O
,	O
8	O
Gbit/s	O
or	O
80	O
Gbit/s	O
is	O
possible	O
depending	O
on	O
port	O
speed	O
.	O
</s>
<s>
Because	O
EtherChannel	B-Protocol
takes	O
advantage	O
of	O
existing	O
wiring	O
it	O
makes	O
it	O
very	O
scalable	O
.	O
</s>
<s>
All	O
Cisco	O
switches	B-Protocol
have	O
the	O
ability	O
to	O
support	O
EtherChannel	B-Protocol
.	O
</s>
<s>
When	O
an	O
EtherChannel	B-Protocol
is	O
configured	O
all	O
adapters	O
that	O
are	O
part	O
of	O
the	O
channel	O
share	O
the	O
same	O
Layer	O
2	O
(	O
MAC	O
)	O
address	O
.	O
</s>
<s>
This	O
makes	O
the	O
EtherChannel	B-Protocol
transparent	O
to	O
network	O
applications	O
and	O
users	O
because	O
they	O
only	O
see	O
the	O
one	O
logical	O
connection	O
;	O
they	O
have	O
no	O
knowledge	O
of	O
the	O
individual	O
links	O
.	O
</s>
<s>
EtherChannel	B-Protocol
aggregates	O
the	O
traffic	O
across	O
all	O
the	O
available	O
active	O
ports	B-Protocol
in	O
the	O
channel	O
.	O
</s>
<s>
The	O
port	O
is	O
selected	O
using	O
a	O
Cisco-proprietary	O
hash	O
algorithm	O
,	O
based	O
on	O
source	O
or	O
destination	O
MAC	O
addresses	O
,	O
IP	B-Protocol
addresses	I-Protocol
or	O
TCP	B-Protocol
and	I-Protocol
UDP	I-Protocol
port	I-Protocol
numbers	O
.	O
</s>
<s>
The	O
hash	O
function	O
gives	O
a	O
number	O
between	O
0	O
and	O
7	O
,	O
and	O
the	O
following	O
table	O
shows	O
how	O
the	O
8	O
numbers	O
are	O
distributed	O
among	O
the	O
2	O
to	O
8	O
physical	O
ports	B-Protocol
.	O
</s>
<s>
In	O
the	O
hypothesis	O
of	O
real	O
random	O
hash	O
algorithm	O
,	O
2	O
,	O
4	O
or	O
8	O
ports	B-Protocol
configurations	O
lead	O
to	O
fair	O
load-balancing	O
,	O
whereas	O
other	O
configurations	O
lead	O
to	O
unfair	O
load-balancing	O
.	O
</s>
<s>
Fault-tolerance	O
is	O
another	O
key	O
aspect	O
of	O
EtherChannel	B-Protocol
.	O
</s>
<s>
Should	O
a	O
link	O
fail	O
,	O
the	O
EtherChannel	B-Protocol
technology	O
will	O
automatically	O
redistribute	O
traffic	O
across	O
the	O
remaining	O
links	O
.	O
</s>
<s>
Spanning	B-Protocol
tree	I-Protocol
protocol	I-Protocol
(	O
STP	O
)	O
can	O
be	O
used	O
with	O
an	O
EtherChannel	B-Protocol
.	O
</s>
<s>
Without	O
the	O
use	O
of	O
an	O
EtherChannel	B-Protocol
,	O
STP	O
would	O
effectively	O
shutdown	O
any	O
redundant	O
links	O
between	O
switches	B-Protocol
until	O
one	O
connection	O
goes	O
down	O
.	O
</s>
<s>
This	O
is	O
where	O
an	O
EtherChannel	B-Protocol
is	O
most	O
desirable	O
,	O
it	O
allows	O
use	O
of	O
all	O
available	O
links	O
between	O
two	O
devices	O
.	O
</s>
<s>
EtherChannels	B-Protocol
can	O
be	O
also	O
configured	O
as	O
VLAN	B-General_Concept
trunks	I-General_Concept
.	O
</s>
<s>
If	O
any	O
single	O
link	O
of	O
an	O
EtherChannel	B-Protocol
is	O
configured	O
as	O
a	O
VLAN	B-General_Concept
trunk	O
,	O
the	O
entire	O
EtherChannel	B-Protocol
will	O
act	O
as	O
a	O
VLAN	B-General_Concept
trunk	O
.	O
</s>
<s>
Cisco	B-Protocol
ISL	I-Protocol
,	O
VTP	B-Protocol
and	O
IEEE	O
802.1Q	O
are	O
compatible	O
with	O
EtherChannel	B-Protocol
.	O
</s>
<s>
A	O
limitation	O
of	O
EtherChannel	B-Protocol
is	O
that	O
all	O
the	O
physical	O
ports	B-Protocol
in	O
the	O
aggregation	O
group	O
must	O
reside	O
on	O
the	O
same	O
switch	O
except	O
in	O
the	O
case	O
of	O
a	O
switch	B-Protocol
stack	I-Protocol
,	O
where	O
they	O
can	O
reside	O
on	O
different	O
switches	B-Protocol
on	O
the	O
stack	O
.	O
</s>
<s>
Avaya	O
's	O
SMLT	O
protocol	O
removes	O
this	O
limitation	O
by	O
allowing	O
the	O
physical	O
ports	B-Protocol
to	O
be	O
split	O
between	O
two	O
switches	B-Protocol
in	O
a	O
triangle	O
configuration	O
or	O
4	O
or	O
more	O
switches	B-Protocol
in	O
a	O
mesh	O
configuration	O
.	O
</s>
<s>
Cisco	O
's	O
Virtual	O
Switching	O
System	O
(	O
VSS	O
)	O
allows	O
the	O
creation	O
of	O
a	O
Multichassis	O
Etherchannel	B-Protocol
(	O
MEC	O
)	O
similar	O
to	O
the	O
DMLT	B-Protocol
protocol	O
allowing	O
ports	B-Protocol
to	O
be	O
aggregated	O
towards	O
different	O
physical	O
chassis	O
that	O
form	O
a	O
single	O
virtual	O
switch	O
entity	O
.	O
</s>
<s>
Cisco	O
Nexus	O
series	O
of	O
switches	B-Protocol
allow	O
the	O
creation	O
of	O
a	O
(	O
vPC	O
)	O
between	O
a	O
remote	O
device	O
and	O
two	O
individual	O
Nexus	O
switches	B-Protocol
.	O
</s>
<s>
The	O
two	O
Cisco	O
Nexus	O
switches	B-Protocol
involved	O
in	O
a	O
vPC	O
differ	O
from	O
stacking	O
or	O
VSS	O
technology	O
in	O
that	O
stacking	O
and	O
VSS	O
create	O
a	O
single	O
data	O
and	O
control	O
plane	O
across	O
the	O
multiple	O
switches	B-Protocol
,	O
whereas	O
vPC	O
creates	O
a	O
single	O
data	O
plane	O
across	O
the	O
two	O
Nexus	O
switches	B-Protocol
while	O
keeping	O
the	O
two	O
control	O
planes	O
separate	O
.	O
</s>
<s>
EtherChannel	B-Protocol
is	O
made	O
up	O
of	O
the	O
following	O
key	O
elements	O
:	O
</s>
<s>
Ethernet	O
links	O
EtherChannel	B-Protocol
works	O
over	O
links	O
defined	O
by	O
the	O
IEEE	O
802.3	O
standard	O
,	O
including	O
all	O
sub-standards	O
.	O
</s>
<s>
All	O
links	O
in	O
a	O
single	O
EtherChannel	B-Protocol
must	O
be	O
the	O
same	O
speed	O
.	O
</s>
<s>
Compatible	O
hardware	O
the	O
entire	O
line	O
of	O
Cisco	B-Device
Catalyst	I-Device
switches	I-Device
as	O
well	O
as	O
Cisco	B-Protocol
IOS	I-Protocol
software-based	O
routers	O
support	O
EtherChannel	B-Protocol
.	O
</s>
<s>
Configuring	O
an	O
EtherChannel	B-Protocol
between	O
a	O
switch	O
and	O
a	O
computer	O
requires	O
support	O
built	O
into	O
the	O
operating	O
system	O
;	O
FreeBSD	O
,	O
for	O
example	O
,	O
supports	O
EtherChannel	B-Protocol
via	O
LACP	O
.	O
</s>
<s>
Multiple	O
EtherChannels	B-Protocol
per	O
device	O
are	O
supported	O
;	O
the	O
number	O
depends	O
on	O
the	O
type	O
of	O
equipment	O
.	O
</s>
<s>
Catalyst	B-Device
6500	I-Device
and	O
6000	O
switches	B-Protocol
support	O
a	O
maximum	O
of	O
64	O
EtherChannels	B-Protocol
.	O
</s>
<s>
Configuration	O
an	O
EtherChannel	B-Protocol
must	O
be	O
configured	O
using	O
the	O
Cisco	B-Protocol
IOS	I-Protocol
on	O
switches	B-Protocol
and	O
router	O
,	O
and	O
using	O
specific	O
drivers	O
when	O
connecting	O
a	O
server	O
.	O
</s>
<s>
There	O
are	O
two	O
main	O
ways	O
an	O
EtherChannel	B-Protocol
can	O
be	O
set	O
up	O
.	O
</s>
<s>
The	O
first	O
is	O
by	O
manually	O
issuing	O
a	O
command	O
on	O
each	O
port	O
of	O
the	O
device	O
that	O
is	O
part	O
of	O
the	O
EtherChannel	B-Protocol
.	O
</s>
<s>
This	O
must	O
be	O
done	O
for	O
the	O
corresponding	O
ports	B-Protocol
on	O
both	O
sides	O
of	O
the	O
EtherChannel	B-Protocol
.	O
</s>
<s>
The	O
second	O
way	O
is	O
using	O
Cisco	O
Port	B-Protocol
Aggregation	I-Protocol
Protocol	I-Protocol
(	O
PAgP	B-Protocol
)	O
for	O
the	O
automated	O
aggregation	O
of	O
Ethernet	O
ports	B-Protocol
.	O
</s>
<s>
EtherChannel	B-Protocol
and	O
IEEE	B-Architecture
802.3ad	I-Architecture
standards	O
are	O
very	O
similar	O
and	O
accomplish	O
the	O
same	O
goal	O
.	O
</s>
<s>
There	O
are	O
a	O
few	O
differences	O
between	O
the	O
two	O
,	O
other	O
than	O
the	O
fact	O
that	O
EtherChannel	B-Protocol
is	O
Cisco	O
proprietary	O
and	O
802.3ad	B-Architecture
is	O
an	O
open	O
standard	O
,	O
listed	O
below	O
:	O
</s>
<s>
EtherChannel	B-Protocol
supports	O
both	O
LACP	O
and	O
Cisco	B-Protocol
's	I-Protocol
PAgP	I-Protocol
,	O
whereas	O
802.3ad	B-Architecture
uses	O
LACP	O
.	O
</s>
<s>
LACP	O
allows	O
for	O
up	O
to	O
8	O
active	O
and	O
8	O
standby	O
links	O
,	O
whereas	O
PAgP	B-Protocol
only	O
allows	O
for	O
8	O
active	O
links	O
.	O
</s>
