In EtherChannel,
you can combine multiple physical links between switches into a single
logical link to increase the bandwidth size. You can combine maximum
eight physical links into one etherchannel link for the purpose of high
speed communication and load balancing between switches.
Etherchannel can be configured using one of these modes.
Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP)
We
will configure here only PAgP in detail and the remaining protocol will
be discussed in the next tips.
Port
Aggregation Protocol is a Cisco proprietary protocol and manage
dynamically negotiates the formation of a channel. You can use following
combination to create etherchannel using PAgP.
desirable on Switch-1 - desirable on Switch-2
auto on Switch-1 - desirable on Switch-2
desirable on Switch-1 - auto on Switch-2
Follow the topology of two switches networks in the given figure for
etherchannel:
Configuration on Switch-A
First run the Show interface trunk command to verify the trunk
links.
Switch-A# Show interface trunk
Port Mode
Encapsulation Status Native
vlan
Fa0/1 desirable n-isl
trunking 1
Fa0/2 desirable n-isl
trunking 1
Fa0/3 desirable n-isl
trunking 1
Port Vlans allowed on trunk
Fa0/1 1-4094
Fa0/2 1-4094
Fa0/3 1-4094
Port Vlans allowed and active in
management domain
Fa0/1 1
Fa0/2 1
Fa0/3 1
Port Vlans in spanning tree forwarding
state and not pruned
Fa0/1 1
Fa0/2 1
Fa0/3 1
Ports
fastethernet 0/1 - 3 to be configured in the etherchannel:
Switch-A(config)#interface range fastEthernet 0/1 -3
Switch-A(config-if-range)#
channel-protocol pagp
Configure
the PAgP protocol to be used in this channel
Switch-A(config-if-range)# channel-group 1 mode desirable
Configure the mode desirable to be used in PAgP
Configuration on Switch-A
Ports
fastethernet 0/1 - 3 to be configured in the etherchannel:
Switch-B(config)#interface range fastEthernet 0/1 -3
Switch-B(config-if-range)#
channel-protocol pagp
Configure the PAgP protocol to be used in this channel
Switch-B(config-if-range)# channel-group 1 mode auto
Configure the mode auto to be used in PAgP
Now
run show command to display the etherchannel configurations on Switch-B
and Switch-A.
Switch-B#show
etherchannel 1 summary
Flags: D - down P - in
port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3
S - Layer2
u - unsuitable for bundling
U - in use
f - failed to allocate aggregator
d - default port
Number of channel-groups in use: 1
Number of aggregators:
1
Group Port-channel Protocol Ports
------+-------------+-----------+---------------------------------
1
Po1(SU) PAgP
Fa0/1(P) Fa0/2(P) Fa0/3(P
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