CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
Layer 2 EtherChannel
A Note On Section Initial Configuration Files: You must load the
initial configuration files for the section, named Basic Layer2
Switching, which can be found in
. Reference the Virtual Routers & Physical
Switches Diagram to complete this task.
Task
Configure Layer 2 EtherChannels between SW1 and all other switches as follows:
Do not use any negotiation protocols.
SW1 should initiate 802.1q trunking negotiation.
Use port-channel numbers in the format of 1Y, where Y is the switch number
for SW2, SW3, and SW4.
Configuration
SW1:
interface range FastEthernet0/19 - 20
channel-group 13 mode on
!
interface range FastEthernet0/21 - 22
channel-group 14 mode on
!
interface range FastEthernet0/23 - 24
channel-group 12 mode on
!
interface Port-channel12
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
!
interface Port-channel13
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
!
interface Port-channel14
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
SW2:
interface range FastEthernet0/23 - 24
channel-group 12 mode on
SW3:
interface range FastEthernet0/19 - 20
channel-group 13 mode on
SW4:
interface range FastEthernet0/21 - 22
channel-group 14 mode on
Verification
For an EtherChannel to form, all member interfaces must have the same
configuration, and both ends of the channel must agree on the same negotiation
protocol; in this case there is no negotiation used between the switches forming the
EtherChannel. In the below
show etherchannel summary
output, the Protocol field is
null, which means that no negotiation was used. This comes from the on mode of
the
channel-group
command. This output also shows that the port-channel is in the
SU state, which means that it is Layer 2 and up; member ports are in the P state,
which means that interfaces have successfully joined the EtherChannel.
SW1#show etherchannel summary
Flags: D - downP - 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: 3
Number of aggregators:3
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
12Po12(SU)-Fa0/23(P) Fa0/24(P)
13Po13(SU)
-Fa0/19(P)
Fa0/20(P)
14Po14(SU)
-Fa0/21(P)
Fa0/22(P)
!
!SW1#show etherchannel protocol
Channel-group listing:
----------------------
Group: 12
----------Protocol:
- (Mode ON)
Group: 13
----------Protocol:
- (Mode ON)
Group: 14
----------Protocol:
- (Mode ON)
As interfaces have been bundled into EtherChannels, the switch will show the
logical interface as being trunk, not the physical interface; also, from STP
perspective, STP will run over the logical interface as well.
SW1#show interfaces trunk
PortMode
Encapsulation
Status
Native vlan
Po12desirable
802.1q
trunking
1
Po13desirable
802.1q
trunking
1
Po14desirable
802.1q
trunking
1
PortVlans allowed on trunk
Po121-4094
Po131-4094
Po141-4094
<output omitted>
!
!SW1#show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root IDPriority
32769
Address
0013.605f.f000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32769 (priority 32768 sys-id-ext 1)
Address0013.605f.f000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1Desg FWD 19128.3 P2p Po12
Desg FWD 12
128.152
P2p Po13
Desg FWD 12
128.160
P2p Po14
Desg FWD 12
128.168
P2p
Verify that physical interfaces have inherited the configuration from the logical
interface, which is the port-channel.
SW1#show interfaces fastEthernet0/19 switchport
Name: Fa0/19
Switchport: EnabledAdministrative Mode: dynamic desirable
Operational Mode: trunk (member of bundle Po13)
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Another way to verify that a Layer 2 channel is working correctly is to view the
spanning-tree topology. If STP runs over the logical port-channel interface instead of
the physical interfaces, channeling has occurred properly. This is because without
channeling, some member interfaces would be in the STP forwarding state and some
blocking, but with channeling all interfaces have the same STP state and role as
displayed by the logical port-channel interface. Note that STP port states and roles
may differ from the output below based on which switch is the STP root bridge.
SW2#show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root IDPriority
32769
Address
000a.b832.3a80
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32769 (priority 32768 sys-id-ext 1)
Address000a.b832.3a80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/19Desg FWD 19
128.21 P2p
Fa0/20Desg FWD 19
128.22 P2p
Fa0/21Desg FWD 19
128.23 P2p
Fa0/22Desg FWD 19
128.24 P2p Po12Desg FWD 12128.152 P2p
!
!SW3#show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root IDPriority
32769
Address
000a.b832.3a80
Cost
19
Port
23 (FastEthernet0/21)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32769 (priority 32768 sys-id-ext 1)
Address0022.5627.1f80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1Desg FWD 19
128.3 P2p
Fa0/21Root FWD 19
128.23 P2p
Fa0/22Altn BLK 19
128.24 P2p
Fa0/23Altn BLK 19
128.25 P2p
Fa0/24Altn BLK 19
128.26 P2p Po13Altn BLK 12128.160 P2p
!
!SW4#show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root IDPriority
32769
Address
000a.b832.3a80
Cost
19
Port
21 (FastEthernet0/19)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32769 (priority 32768 sys-id-ext 1)
Address001a.a174.2500
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1Desg FWD 19
128.3 P2p
Fa0/19Root FWD 19
128.21 P2p
Fa0/20Altn BLK 19
128.22 P2p
Fa0/23Desg FWD 19
128.25 P2p
Fa0/24Desg FWD 19
128.26 P2p Po14Altn BLK 12128.168 P2p