CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
Layer 2 EtherChannel with PAgP
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:
Use Cisco’s proprietary protocol for negotiation.
Only SW1 should actively initiate the EtherChannel negotiation.
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 desirable
!
interface range FastEthernet0/21 - 22
channel-group 14 mode desirable
!
interface range FastEthernet0/23 - 24
channel-group 12 mode desirable
!
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 auto
SW3:
interface range FastEthernet0/19 - 20
channel-group 13 mode auto
SW4:
interface range FastEthernet0/21 - 22
channel-group 14 mode auto
Verification
Port Aggregation Protocol (PAgP) is a Cisco proprietary negotiation protocol for
EtherChannel links. The desirable mode of PAgP, like DTP, is used to initiate
negotiation, whereas the auto mode is used to listen for negotiation. This implies
that one side running desirable with the other side running desirable or auto will
result in a channel being formed, but both sides running auto will not. Verify that
EtherChannel has been successfully negotiated and the protocol used is PAgP.
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)
PAgPFa0/23(P)
Fa0/24(P)
13Po13(SU)
PAgPFa0/19(P)
Fa0/20(P)
14Po14(SU)
PAgPFa0/21(P)
Fa0/22(P)
!
!SW1#show etherchannel protocol
Channel-group listing:
----------------------
Group: 12
----------Protocol: PAgP
Group: 13
----------Protocol: PAgP
Group: 14
----------Protocol: PAgP
Verify that SW1 is configured for desirable mode, and all other switches for auto
mode.
SW1#show etherchannel 12 port-channel
Port-channels in the group:
---------------------------
Port-channel: Po12
------------
Age of the Port-channel = 0d:03h:01m:55s
Logical slot/port
= 2/12
Number of ports = 2
GC
= 0x000C0001
HotStandBy port = null
Port state= Port-channel Ag-Inuse
Protocol= PAgP
Port security= Disabled
Ports in the Port-channel:
Index Load PortEC stateNo of bits
------+------+------+------------------+----------- 000Fa0/23 Desirable-Sl
0 000Fa0/24 Desirable-Sl
0
Time since last port bundled:0d:03h:01m:46s Fa0/24
!
!SW2#show etherchannel 12 port-channel
Port-channels in the group:
---------------------------
Port-channel: Po12
------------
Age of the Port-channel = 0d:03h:02m:02s
Logical slot/port
= 2/12
Number of ports = 2
GC
= 0x000C0001
HotStandBy port = null
Port state= Port-channel Ag-Inuse
Protocol= PAgP
Port security= Disabled
Ports in the Port-channel:
Index Load PortEC stateNo of bits
------+------+------+------------------+----------- 000Fa0/23 Automatic-Sl
0 000Fa0/24 Automatic-Sl
0
Time since last port bundled:0d:03h:02m:00s Fa0/24
Verify that trunking has been negotiated and logical port-channel interfaces are
used by STP.
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 IDPriority32769
Address
000a.b832.3a80
Cost
12
Port
152 (Port-channel12)
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
Root FWD 12
128.152
P2p Po13
Desg FWD 12
128.160
P2p Po14
Desg FWD 12
128.168
P2p
Verify the EtherChannel state on all switches. However, because switches use a
negotiation protocol, if EtherChannel shows as functional on one side, it has to be
functional on the other side as well. With no negotiation protocol being used,
EtherChannel may not actually be functional from the perspective of both switches,
and you must verify that.
SW2#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: 1
Number of aggregators:1
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
12Po12(SU)PAgPFa0/23(P) Fa0/24(P)
!
!SW3#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: 1
Number of aggregators:1
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
13Po13(SU)PAgPFa0/19(P) Fa0/20(P)
!
!SW4#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: 1
Number of aggregators:1
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
14Po14(SU)PAgPFa0/21(P) Fa0/22(P)
Verify that physical interfaces have inherited the configuration from the logical
interface—for example, FastEthernet0/19 of SW1.
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
If configuration is done on one side of the EtherChannel only, for example, only on
SW1, because PAgP negotiation will fail, the following messages will be logged:
%EC-5-L3DONTBNDL1: Fa0/19 suspended: PAgP not enabled on the remote port.
%EC-5-L3DONTBNDL1: Fa0/20 suspended: PAgP not enabled on the remote port.
To avoid any problems in the network, physical interfaces will be logically disabled
at Layer 2 and will appear in the suspended state for the EtherChannel.
SW1#show etherchannel summary
Flags: D - downP - bundled in port-channelI - stand-alones - 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 ProtocolPorts
------+-------------+-----------+-----------------------------------------------
13Po13(SU)PAgPFa0/19(s) Fa0/20(s)
!
!SW1#show ip interface brief | i 19|20
FastEthernet0/19
unassigned
YES manual updown
FastEthernet0/20
unassigned
YES manual updown