Configuring an EtherChannel
Etherchannel’s are used to build redundant links and bundle multiple links to increase aggregate bandwidth. This lab will discuss and demonstrate the configuration and verification of static etherchannel links.
Real World Application & Core Knowledge
Ether-Channel is an extremely common technology used in the real world to provide redundancy and port aggregation. For example you have 2 NIC’s in a Server and you want to configure them to work simultaneously with each other. Ether-Channel technology gives you the ability to “bundle” multiple physical links into a single logical link.
There are 3 types of EtherChannel’s. The first one which is the most common for port density aggregation from switch to switch is called called an “unconditional” or static EtherChannel. From a technical perspective; the mode is “on”. This is the type of EtherChannel that this lab will concentrate on however the other two types of EtherChannel technologies are Link Aggregation Control Protocol (LACP) and Port Aggregation Protocol (PAgP).
LACP is the IEEE Standard and is the most common dynamic ether-channel protocol, whereas PAgP is a Cisco proprietary protocol and works only between supported vendors and Cisco devices.
Note that Ether-channel technology is general allows for multi-link aggregation, redundancy and load balancing. LACP and PAgP are dynamic ether-channel protocols that allows for dynamic creation of an EtherChannel. LACP, PAgP and Static EtherChannel’s are not compatible with one another. LACP and PAgP will be discussed in the new two labs.
Keep in mind when using LACP and/or PAgP, the devices use more resources to dynamically create a channel such as processing the aggregation protocol frames and actually creating the channel itself, however when using a static EtherChannel, this downfall does NOT exist.
Another great example of an ether-channel is two switches inter-connected with two or more links. Due to spanning-tree operations (which will be discussed in another lab); only one of the links will be fowarding at any given time to prevent layer two loops known as broadcast storms. If you have two or more links in an ether-channel, the multiple links appear as a single logical link and is utilized as such by the device which includes spanning-tree and therefore the single logical link will forward traffic. Keep in mind if you have two ether-channels with two links between two of the same switches, one logical link (the ether-channel) will be blocked by Spanning tree to prevent broadcast storms.
EtherChannel load balancing can be based several configurable options which include destination ip, destination mac address, source XOR destination IP address, source XOR destination mac address, source ip address or source mac address.
In this lab you will familiarize yourself with the following commands;
| Command | Description |
|---|---|
| channel-group # mode on | This command when execute in interface configuration mode assigns that particular interface to a channel group number specified and sets the EtherChannel mode to unconditional as stated by the “on” |
| show etherchannel summary | This command when executed from user or privileged mode will display a summary of local EtherChannel(s) properties such as the channel-group number, ports in the channel group, and the role the ports the play. |
| show etherchannel detail | This command when executed from user or privileged mode will display detailed information relating to the EtherChannel(s) local to the device. |
| show etherchannel port-channel | This command when executed from user or privileged mode will display the EtherChannel’s logical port-channel group interface properties. This will be discussed in more detail in Lab 4-6. |
Lab Prerequisites
- If you are using GNS3 than load the Free CCNA Workbook GNS3 topology than start devices;R1, R2, SW1 and SW2.
- Establish a console session with devices R1, R2, SW1 and SW2 than configure the devices respected hostname(s).
- Configure R1’s FastEthernet0/0 interface with the IP Address 10.1.1.1/24 and R2’s FastEthernet0/1 interface with the IP address of 10.1.1.2/24
- Create VLAN 10 as a layer 2 VLAN on both SW1 and SW2. (Layer 2 VLAN’s do not have Layer 3 VLAN interfaces representing the VLAN; ie, no interface Vlan10.)
- Place both SW1’s FastEthernet0/1 and SW2’s FastEthernet0/2 interfaces into VLAN 10.
- Configure Interfaces Fa0/10, Fa0/11 and Fa0/12 on SW1 and SW2 to trunk.
Lab Objectives
- Configure Interfaces FastEthernet0/10, FastEthernet0/11 and FastEthernet0/12 on both SW and SW2 as an unconditional EtherChannel.
- Verify that all three interfaces are indeed participating in the EtherChannel by using the show etherchannel summary command.
- Determine what type of load balancing is used on the EtherChannel 1 by using the show etherchannel load-balance
- Verify the operation of the EtherChannel trunk link by verifying ip communication between R1 and R2 using the ping command.
Lab Instruction
Step 1 – Configure Interfaces FastEthernet0/10, FastEthernet0/11 and FastEthernet0/12 on both SW and SW2 as an unconditional EtherChannel.
This is done by using the channel-group # mode on command in interface or interface range configuration mode as shown below;
SW1 con0 is now available Press RETURN to get started. SW1>enable SW1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. SW1(config)#interface range fa0/10 - 12 SW1(config-if-range)#no shut SW1(config-if-range)#channel-group 1 mode on Creating a port-channel interface Port-channel1 SW1(config-if-range)# %EC-5-BUNDLE: Interface Fa0/10 joined port-channel Po1 %EC-5-BUNDLE: Interface Fa0/11 joined port-channel Po1 %EC-5-BUNDLE: Interface Fa0/12 joined port-channel Po1 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up SW1(config-if-range)#end SW1#
SW2 con0 is now available Press RETURN to get started. SW2>enable SW2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. SW2(config)#interface range fa0/10 - 12 SW2(config-if-range)#no shut SW2(config-if-range)#channel-group 1 mode on Creating a port-channel interface Port-channel1 SW2(config-if-range)# %EC-5-BUNDLE: Interface Fa0/10 joined port-channel Po1 %EC-5-BUNDLE: Interface Fa0/11 joined port-channel Po1 %EC-5-BUNDLE: Interface Fa0/12 joined port-channel Po1 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up SW2(config-if-range)#end SW2#
Step 2. – Verify that all three interfaces indeed participate in the EtherChannel by using the show etherchannel summary command.
SW1#show etherchannel summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
R - Layer3 S - Layer2
U - in use
Group Port-channel Ports
-----+------------+---------------------------------------------
1 Po1(SU) Fa0/10(P) Fa0/11(P) Fa0/12(P)
SW1#
SW2#show etherchannel summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
R - Layer3 S - Layer2
U - in use
Group Port-channel Ports
-----+------------+---------------------------------------------
1 Po1(SU) Fa0/10(P) Fa0/11(P) Fa0/12(P)
SW2#
Step 3. – Determine what type of load balancing is used on the EtherChannel 1 by using the show etherchannel load-balance as shown below;
SW1#show etherchannel load-balance
EtherChannel Load-Balancing Configuration:
src-mac
EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source MAC address
IPv4: Source MAC address
IPv6: Source MAC address
SW1#
Step 4. – Verify the operation of the EtherChannel trunk link by verifying ip communication between R1 and R2 using the ping command.
You must complete the pre-requisites before this verification can be successful. Once completely correctly R1 should Ping R2 by traversing the EtherChannel.
R1#ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 4/23/52 ms
R1#
If you want to perform additional verification you can shutdown interfaces Fa0/11 and Fa0/12 on SW1 and ensure that the R1 still has IP connectivity to R2 as shown below;
SW1#config terminal SW1#interface range f0/11 - 12 SW1#shutdown SW1#end SW1# Configured from console by console SW1# %LINK-5-CHANGED: Interface FastEthernet0/11, changed state to administratively down %LINK-5-CHANGED: Interface FastEthernet0/12, changed state to administratively down %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/11, changed state to down SW1# %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/12, changed state to down SW1#
After shutting down two of the three interfaces in the etherchannel you’ll still have ip communication between R1 and R2 as shown below;
R1#ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
R1#
