COMPUTER TIPS

How to configure EtherChannel using PAgP protocol?

 

 

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-B

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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