Configuring a PAgP EtherChannel

PAgP was the precursor to LACP, developed by Cisco for link aggregation between network nodes to form redundant resiliant links. This lab will discuss and demonstrate the configuration and verification of PaGP EtherChannel.

Real World Application & Core Knowledge

In the world of EtherChannel technology there are two types of dynamic channel-group protocols, Port Aggregation Protocol (PAgP) which is a Cisco Proprietary protocol and Link Aggregation Control Protocol (LACP) which is the IEEE standard.

PAgP uses two types of port modes; auto and desirable. PAgP mode desirable attempts to initiate a PAgP dynamic ether-channel whereas auto does not but accepts PAgP initiation attempts from a device set to desirable.

In this lab you will familiarize yourself with the following commands;

Command	Description
channel-group # mode desirable	This command when executed in interface configuration mode sets the channel-group number and PAgP mode to aggressively attempt to form a PAgP EtherChannel. If negotiations fail, the EtherChannel will not pass traffic.
channel-group # mode auto	This command when executed in interface configuration mode sets the channel-group number and PAgP mode to listen for PAgP packets but not aggressively negotiate a PAgP EtherChannel.
show etherchannel summary	This command when executed from user or privileged mode will display a summary of local EtherChannel(s) properties such as the channel-group number, ports in the channel group, and the role the ports the play.
show etherchannel detail	This command when executed from user or privileged mode will display detailed information relating to the EtherChannel(s) local to the device.

Lab Prerequisites

Establish a console session with devices R1, R2, SW1 and SW2 than configure the devices respected hostname(s).
Configure interfaces Fa0/10, Fa0/11 and Fa0/12 on both SW1 and SW2 as dot1q trunks.
Configure VLAN 10 on both SW1 and SW2 and assign R1 and R2’s switch ports to VLAN 10.
Assign the IP address 10.1.1.1/24 to R1’s FastEthernet0/0 interface and 10.1.1.2/24 to R2’s FastEthernet0/1 interface.

Lab Objectives

Configure SW1’s Fa0/10, Fa0/11 and Fa0/12 interfaces to aggressively attempt to form a PAgP EtherChannel.
Configure SW2’s Fa0/10, Fa0/11 and Fa0/12 interfaces to form a PAgP EtherChannel when a device attempts to negotiate a PAgP EtherChannel only.
Verify that interfaces Fa0/10, Fa0/11 and Fa0/12 on SW1 formed a PAgP EtherChannel correctly.
Ping R2’s FastEthernet0/0 interface from R1 to verify communications between the switches.

The NM-16ESW used in the Free CCNA Workbook GNS3 Topology for SW1, SW2 and SW3 does not support the Ether-Channel Port Aggregation Protocol (PAgP). This Lab instructional section is demonstrated using two Cisco Catalyst 3560 Series switches.

Lab Instruction

Step 1 . – Configure SW1’s Fa0/10, Fa0/11 and Fa0/12 interfaces to aggressively attempt to form a PAgP EtherChannel.

For this you’ll use the channel-group # mode desirable command in interface or interface range configuration mode as shown below;

SW1 con0 is now available



Press RETURN to get started.



SW1>enable
SW1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
SW1(config)#interface range f0/10 - 12
SW1(config-if-range)#channel-group 1 mode desirable
Creating a port-channel interface Port-channel 1
SW1(config-if-range)#no shut
SW1(config-if-range)#end
SW1#

Step 2. – Configure SW2’s Fa0/10, Fa0/11 and Fa0/12 interfaces to form a PAgP EtherChannel when a device attempts to negotiate a PAgP EtherChannel only.

For this you’ll use the channel-group # mode auto command in interface or interface range configuration mode as shown below;

SW2 con0 is now available



Press RETURN to get started.



SW2>enable
SW2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
SW2(config)#interface range f0/10 - 12
SW2(config-if-range)#channel-group 1 mode auto
Creating a port-channel interface Port-channel 1
SW2(config-if-range)#no shut
SW2(config-if-range)#end
SW2#

Step 3. – Verify that interfaces Fa0/10, Fa0/11 and Fa0/12 on SW1 formed a PAgP EtherChannel correctly.

To verify your configuration you can use either the show etherchannel summary or show etherchannel detail command in user or privileged mode as shown below;

SW1#show etherchannel summary
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Fa0/10(P)   Fa0/11(P)   Fa0/12(P)   

SW1#

Step 4. – Ping R2’s FastEthernet0/0 interface from R1 to verify communications between the switches as shown below;

R1#ping 10.1.1.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 1/2/4 ms
R1#

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