Etherchannel/port-channel

alexnetwork

On different Cisco switches it is possible to create
logical connections that
are made-up off
different fysical interface. It is needed that these
interface
do have the
same speed.

Most Cisco switches support max 64 etherchannels.
These interfaces do not have to be contiguous.
or even on the
same module. Each channel must be made up of min 2, max 8 interfaces.
The best is to use 2 ,4 or 8
interfaces. This will give the perfect load-balancing.

The load-balancing can be bases on layer 2/3 or 4
information.
It is not possible to have different load-balancing methods
for different Etherchannels
on one switch.
If the load-balancing method is change, it is applicable for all.
The load-balancing method can be:
-         
src-mac
-         
dst-mac
-         
src-dst-mac
-         
src-ip
-         
dst-ip
-         
src-dst-ip
-         
src-port
-         
dst-port
-         
src-dst-port

By using port-channel
load-balance {option}> it is possible to change to method.
If a single header is used to load-balance the
low-order bits is used to dictate to
witch interface
the frame is send. If two headers are used a XOR function is used on
the low-order
bits.

It is possible to change what path with-in the etherchannel a frame takes by used the following command:
test etherchannel load-balance interface port-channel [#] ip [src] [dst]>

to assign a
physical interface towards a port-channel use the following command:
channel-group [#] mode on

There are two type of dynamic
protocols to negotiate an etherchannels: PAgP and LACP 8021.AD
PAgP is Cisco proprietary
When these protocols start to communicate there is an
exchange of information before the port-channel can be formed. The following
items must match before a port-channel can form:
-         
same speed/duplex
-         
Access VLAN (if not trunked)
-         
Same trunking
type, allowed VLAN and native VLAN (if trunked)
-         
Each port must have the same STP
cost per VLAN with-in the portchannel
-         
No SPAN ports

channel-group [#] mode on (disables PAgP en LACP)
channel-group
[#] mode off (disables PAgP en LACP and prevent the ports to form a port-channel)
channel-group
[#] mode auto (use PAgP in a passive mode, it will wait until a PAgP packet will be send)
channel-group
[#] mode passive (use LACP in a
passive mode, it will wait until a PAgP packet will
be send)
channel-group
[#] mode desirable (use PAgP in an active mode, it will start to send  PAgP packets)
channel-group
[#] mode active (use LACP in an
active mode, it will start to send  LACP
packets)

3750(config)#interface range gigabitethernet 1/0/2 - 43750(config-if-range)#channel-group 1 mode on3750(config-if-range)#switchport3750(config-if-range)#switchport trunk encapsulation dot1q3750(config-if-range)#switchport mode trunkFirst type the channel-group command. After that all interface commands will be automatically duplicated on all the interfaces group in the channel-group.

With LACP it is possible to create a port-channel on a
stack (3560/3750 switches).
This is based on IOS version 12.2(25)SEE

Show command’s
·        
show interfaces port-channel [channel-group-number]
·        
show etherchannel [channel-group-number]
summary
Verify command’s

test etherchannel
     load-balance interface port-channel [#] ip [src] [dst
               
               
               

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