EtherChannel Configuration: L2 and L3 Bundling with Load Balancing
Overview
This lab focuses on implementing and verifying EtherChannel technology to combine multiple physical links into logical bundles, thereby enhancing bandwidth and redundancy. Layer 2 EtherChannels were configured using both LACP and PAgP between access and distribution switches, while a Layer 3 EtherChannel was created between the distribution switches using static mode. Load balancing methods were reviewed and updated to utilize both source and destination IP addresses for improved traffic distribution.
| Skills Demonstrated |
|---|
| Configuring Layer 2 EtherChannels using LACP (active mode) |
| Configuring Layer 2 EtherChannels using PAgP (desirable mode) |
| Implementing Layer 3 static EtherChannel with routed ports |
| Verifying EtherChannel states using summary commands |
| Modifying and confirming EtherChannel load-balancing behavior |
| Establishing IP routing and configuring static routes for inter-VLAN communication |
| Testing end-to-end connectivity across the topology |
| Tools Used |
|---|
| Cisco Packet Tracer |
| Switch and Route CLI |
| EtherChannel Summary and Load-Balance Commands |
| Ping Utility |
| Trunk and Routed Interfaces |
1. Network Topology
I have set up a network topology to simulate access layer switches and distribution layer switches. All of the connections between these switches have redundant links, and because of STP, only one link will be active at a time while the other will be a backup.
To have both links be forwarding at the same time and increase potential bandwidth, I will be setting up Layer 2 EtherChannel configuration between the access layer switches (ASW) and the distribution layer switches (DSW), and Layer 3 EtherChannel configuration between the distribution layer switches.
2. Layer 2 EtherChannel Configuration
ASW1 → DSW1 EtherChannel Configuration (LACP)
Starting first on ASW1, looking at the port roles with the "show spanning-tree" command, we can see that G0/1 is the root port and is forwarding and G0/2 is an alternate port and won't forward or receive frames. Once configured with an EtherChannel, they will turn into one port channel interface which will be the root port and forward traffic using both physical interfaces.
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 20481
Address 0007.EC07.1D30
Cost 8
Port 25(GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0005.5E1E.5B9D
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.1 P2p
Gi0/2 Altn BLK 4 128.26 P2p
Gi0/1 Root FWD 4 128.25 P2p
Fa0/2 Desg FWD 19 128.2 P2p
To configure both G0/1 and G0/2 together, I run the following commands and I will be using LACP protocol which allows for an active or passive mode. Once configured with EtherChannel I will also make the new port channel a trunk port.
ASW1> en
ASW1#> conf t
ASW1(config)# int range g0/1 - 2
ASW1(config-if-range)# channel-group 1 mode active
ASW1(config-if-range)# int po1
ASW1(config-if)# switchport mode trunk
Now when running the "show etherchannel summary" command we get the following output:
Flags: D - down P - 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
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(SD) LACP Gig0/1(I) Gig0/2(I)
Now on DSW1, I configure interfaces G1/0/3 and G1/0/4 to be EtherChannel and trunk ports as well:
DSW1> en
DSW1#> conf t
DSW1(config)# int range g1/0/3 - 4
DSW1(config-if-range)# channel-group 1 mode active
DSW1(config-if-range)# int po1
DSW1(config-if)# switchport mode trunk
Now when running the "show etherchannel summary" command on DSW1 we see the following output and a "P" flag letting us know it's set up correctly:
Flags: D - down P - 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
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) LACP Gig1/0/3(P) Gig1/0/4(P)
And when running "show interface trunk" we can see that port Po1 is a trunk port:
Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 1
Port Vlans allowed on trunk
Po1 1-1005
Port Vlans allowed and active in management domain
Po1 1
Port Vlans in spanning tree forwarding state and not pruned
Po1 none
Finally, when running "show spanning-tree" we can see that those interfaces have been replaced with Po1 and are forwarding:
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 20481
Address 0007.EC07.1D30
Cost 4
Port 1(GigabitEthernet1/0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 0002.161B.EBBC
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1 Desg FWD 3 128.29 Shr
Gi1/0/1 Root FWD 4 128.1 P2p
Gi1/0/2 Altn BLK 4 128.2 P2p
ASW2 → DSW2 EtherChannel Configuration (PAgP)
Now I am going to make the same EtherChannel and trunk port configurations from ASW2 to DSW2, except I will be using the PAgP protocol which uses desirable and auto.
I run the following commands on ASW2:
ASW2> en
ASW2#> conf t
ASW2(config)# int range g0/1 - 2
ASW2(config-if-range)# channel-group 1 mode desirable
ASW2(config-if-range)# int po1
ASW2(config-if)# switchport mode trunk
Then I run the following commands on DSW2:
DSW2> en
DSW2#> conf t
DSW2(config)# int range g1/0/3 - 4
DSW2(config-if-range)# channel-group 1 mode active
DSW2(config-if-range)# int po1
DSW2(config-if)# switchport mode trunk
Now when running the "show etherchannel summary" command on DSW1 we see the following output and a "P" flag letting us know it's set up correctly:
Flags: D - down P - 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
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 Gig1/0/3(P) Gig1/0/4(P)
And when running "show interface trunk" we can see that port Po1 is a trunk port:
Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 1
Port Vlans allowed on trunk
Po1 1-1005
Port Vlans allowed and active in management domain
Po1 1
Port Vlans in spanning tree forwarding state and not pruned
Po1 1
Finally, when running "show spanning-tree" we can see that those interfaces have been replaced with Po1 and are forwarding:
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 20481
Address 0007.EC07.1D30
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 20481 (priority 20480 sys-id-ext 1)
Address 0007.EC07.1D30
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1 Desg FWD 3 128.29 Shr
Gi1/0/1 Desg FWD 4 128.1 P2p
Gi1/0/2 Desg FWD 4 128.2 P2p
3. Layer 3 EtherChannel Configuration
Now I will be configuring EtherChannel between the Layer 3 Switches DSW1 and DSW2 I will use the static mode this time.
I run the following commands first on DSW1:
DSW1> en
DSW1#> conf t
DSW1(config)# int range g1/0/1 - 2
DSW1(config-if-range)# channel-group 2 mode on
Then I run similar command on DSW2:
DSW2> en
DSW2#> conf t
DSW2(config)# int range g1/0/1 - 2
DSW2(config-if-range)# channel-group 2 mode on
Now when running "show spanning-tree" on either DSW1 or DSW2 we can see the EtherChannel active for both channel group 1 and 2:
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 20481
Address 0007.EC07.1D30
Cost 3
Port 30(Port-channel2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 0002.161B.EBBC
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1 Desg FWD 3 128.29 Shr
Po2 Root FWD 3 128.30 Shr
4. IP Addresses and Routing
Now in order to enable routing and a connection from the PCs to the server I must set up IP addresses and routing on the switches. I start running these commands on DSW1:
DSW1> en
DSW1#> conf t
DSW1(config)# int po2
DSW1(config-if)# no switchport
DSW1(config-if)# ip address 10.0.0.1 255.255.255.252
DSW1(config-if)# exit
DSW1(config)# ip routing
DSW1(config-if)# ip route 172.16.2.0 255.255.255.0 10.0.0.2
Now when running "show ip route" on DSW1 we can see the routes:
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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
Gateway of last resort is not set
10.0.0.0/30 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, Port-channel2
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected, Vlan1
S 172.16.2.0 [1/0] via 10.0.0.2
Now I run similar commands on DSW2 to add IP addresses and routing:
DSW2> en
DSW2#> conf t
DSW2(config)# int po2
DSW2(config-if)# no switchport
DSW2(config-if)# ip address 10.0.0.2 255.255.255.252
DSW2(config-if)# exit
DSW2(config)# ip routing
DSW2(config-if)# ip route 172.16.1.0 255.255.255.0 10.0.0.1
Now when running "show ip route" on DSW2 we can see the routes:
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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
Gateway of last resort is not set
10.0.0.0/30 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, Port-channel2
172.16.0.0/24 is subnetted, 2 subnets
S 172.16.1.0 [1/0] via 10.0.0.1
C 172.16.2.0 is directly connected, Vlan1
Now that the IP addresses are configured, PC1 can reach SRV1:
5. EtherChannel Load Balancing
Taking a look at the current load balancing on ASW1, ASW2, DSW1, and DSW2 we can see that it's balancing by src-mac:
ASW1> en
ASW1#> show etherchannel load-balance
EtherChannel Load-Balancing Operational State (src-mac):
Non-IP: Source MAC address
IPv4: Source MAC address
IPv6: Source MAC address
I'm going to load balance by src-dst-ip so I run the following command on ASW1, ASW2, DSW1, and DSW2:
ASW1> en
ASW1#> conf t
ASW1(config)# port-channel load-balance src-dst-ip
Now when running the "show etherchannel load-balance" command we can see it now load balanced by "src-dst-ip":
EtherChannel Load-Balancing Operational State (src-dst-ip):
Non-IP: Source XOR Destination MAC address
IPv4: Source XOR Destination IP address
IPv6: Source XOR Destination IP address