CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
Layer 3 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 3 EtherChannels between SW2 and SW4 as follows:
Use both directly connected Ethernet links.
Use port-channel number 24 and the subnet 155.1.108.Y/24, where Y is the
switch number.
Use an industry standard protocol for negotiation.
Both switches should actively initiate the EtherChannel negotiation.
Ensure that IPv4 reachability is obtained between SW2 and SW4.
Configuration
SW2:
interface Port-channel24
no switchport
ip address 155.1.108.2 255.255.255.0
!
interface range FastEthernet0/19 - 20
no switchport
channel-group 24 mode active
SW4:
interface Port-channel24
no switchport
ip address 155.1.108.4 255.255.255.0
!
interface range FastEthernet0/19 - 20
no switchport
channel-group 24 mode active
Verification
Pitfall
One common problem with forming Layer 3 EtherChannel links is the order of
operations. The important point to remember is that when the
channel-group
command is issued, the attributes of the member interfaces are immediately
inherited by the port-channel interface. This means that if the
channel-group
command is issued before the
no switchport
command on the physical
interfaces, the logical port-channel interface will be created as the default of
Layer 2, and this cannot be changed afterward. A subsequent attempt to
issue the
channel-group
command will generate an error message saying that
the channel interface and the members are not compatible. To resolve this
problem, simply issue the
no switchport
command before the
channel-group
command. If configured properly, the state of the port-channel from the
show etherchannel summary
command should show RU for routed and in use.
SW2#show etherchannel 24 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: 2
Number of aggregators:2
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
24Po24(RU)LACPFa0/19(P) Fa0/20(P)
!
!SW4#show etherchannel 24 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: 2
Number of aggregators:2
Group Port-channel ProtocolPorts
------+-------------+-----------+-----------------------------------------------
24Po24(RU)LACPFa0/19(P) Fa0/20(P)
Verify IPv4 connectivity between SW2 and SW4.
SW4#ping 155.1.108.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 155.1.108.2, timeout is 2 seconds:.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 1/1/1 ms
The port-channel interface should appear as a normal Layer 3 routed interface in
the IPv4 routing table.
SW2#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.SW2(config)#ip routing
!SW2#show ip route connected
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
155.1.0.0/16 is variably subnetted, 2 subnets, 2 masks
C155.1.108.0/24 is directly connected, Port-channel24
L155.1.108.2/32 is directly connected, Port-channel24
Note that a Layer 3 interface in a switch is just a "one-legged" VLAN. SW4 is using
VLAN 1006 internally for this Layer 3 port-channel.
SW2#show vlan internal usage
VLAN Usage
---- --------------------1006 Port-channel24
This is not just for port-channels but also for any Layer 2 port on the switch that is
converted to a Layer 3 port by using the
no switchport
command. The internal
VLAN cannot be used for anything else. The policy that controls how the VLAN
numbers are assigned is managed by the following command:
vlan internal
allocation policy ascending
.
SW2#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.SW2(config)#vlan 1006
SW2(config-vlan)#exit
!
% Failed to create VLANs 1006
VLAN(s) not available in Port Manager.
%Failed to commit extended VLAN(s) changes.
%PM-4-EXT_VLAN_INUSE: VLAN 1006 currently in use by Port-channel24
%SW_VLAN-4-VLAN_CREATE_FAIL: Failed to create VLANs 1006: VLAN(s) not available in Port Manager