EtherChannel
I’ll discuss the CLI because you need to know CLI commands too. Remember, there are two
versions of EtherChannel, the Cisco version and the IEEE version. I’ll show how to use the
Cisco version in this section and bundle the links between the S1 switch and the Core.
I’ll use the interface port-channel global command and the channel-group and
channel-protocol interface commands on the S1 and Core switches. Here (in Table 5.10) are
the commands we’ll use for etherchannel:
Command and Meaning
Command Meaning
interface port-channel Configures the virtual port or interface that will serve as the new
single-bundled interface
channel-group Configures the virtual link that binds the physical interfaces to
the virtual interface bundle
channel-protocol Configures the EtherChannel protocol to be used
Here’s what that looks like:
S1#config t
S1(config)#int port-channel 1
S1(config-if)#int range f0/1-2
S1(config-if-range)#switchport mode trunk
1d03h: %SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/2 moved to
Forwarding (UplinkFast).
S1(config-if-range)#switchport nonegotiate
S1(config-if-range)#channel-group 1 mode desirable
S1(config-if-range)#do sh int fa0/1 etherchannel
Port state = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1 Mode = Desirable-Sl Gcchange = 0
Port-channel = null GC = 0x00010001 Pseudo port-channel = Po1
Port index = 0 Load = 0x00 Protocol = PAgP
[output cut]
Core#config t
Core(config)#int port-channel 1
Core(config-if)#int range f0/7-8
Core(config-if-range)#switchport trunk encap dot1q
Core(config-if-range)#switchport mode trunk
1d03h: %SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/2 moved to
Forwarding (UplinkFast).
Core(config-if-range)#switchport nonegotiate
Core(config-if-range)#channel-group 1 mode desirable
1d04h: %SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/2 moved to
Forwarding (UplinkFast).
1d04h: %SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/2 moved to
Forwarding (UplinkFast).
1d04h: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
1d04h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed
state to up
Core(config-if-range)#do show int port-channel 1
Port-channel1 is up, line protocol is up (connected)
Hardware is EtherChannel, address is 001b.2b55.7501 (bia 001b.2b55.7501)
MTU 1500 bytes, BW 200000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, link type is auto, media type is unknown
[output cut]
I added the switchport nonegotiate interface command to stop the switches from trying
to autodetect the link types and to automatically set up trunking. Instead, I statically configured
my trunk links. The two links between the S1 and the Core are now bundled using the
Cisco EtherChannel version of Port Aggregation Protocol (PAgP).