How to configure EtherChannel ?

Previous post describes how EtherChannel works and why we use it.  
Take a look here

Now we’ll discuss how to configure EtherChannel.

As we seen before, we can bundle up to 8 physical interfaces. We must bind the number of physical interfaces into one logical interface (Channel).  Most of the Cisco switches support 64 channels. Single channel can bind min 2 to max 8 physical interfaces.

PAgP and LACP are the two different Protocols which facilitates the automatic creation of EtherChannels by Exchanging packets between Ethernet interfaces.

PAgP is a Cisco proprietary protocol whereas LACP is an open standard protocol 802.3ad

Two types of EtherChannel Configuration:

1.       1. Layer 3 Configuration: In Layer 3 EtherChannel Configuration, first we must create a logical interface which is call Port-Channel. Then we add the physical interfaces to the Port-Channel.

Example to create a Port-Channel:

Router# configure terminal

Router(config)# interface port-channel 6    (port-channel number 1-64)

Router(config-if)# ip address 10.0.0.1 255.0.0.0

Router(config-if)# exit

Router(config)# exit

Router# show running-config interface port-channel 6  (to verify the port-channel configuration)

We created a port-channel successfully. Now we must add the physical interfaces to this port-channel 6.

Router# configure terminal

Router(config)# interface range fastethernet 1/1 -2

Router(config-if)# no ip address

Router(config-if)# channel-group group 6 mode desirable  (by-defalut Cisco devices use PAgP)

Router(config-if)# exit

Router# show running-config interface fastethernet 1/1  (to verify interface 1 configuration)

 Router# show interfaces fastethernet 1/1 etherchannel

2.       2. Layer 2 Configuration:  Command varies in Layer 2. We manually created port-channel in Layer 3, but in Layer 2 we must create a channel-group which automatically assigns logical port-channel.

Example to create a channel-group:

Switch(config)#interface range fastethernet 1/1 - 4

Switch (config-if-range)#channel-group 1 mode on    (Port 1/1-4 assigned to port-channel)

Switch (config-if-range)#switchport

Switch (config-if-range)#switchport trunk encapsulation dot1q

Switch (config-if-range)#switchport mode trunk

Switch #show interfaces port-channel 1

Switch #show etherchannel 1 summary

In the above example we assigned the ports as trunk. The ports with in a EtherChannel must be in trunk mode or in a single VLAN.

Whatever change of configurations made on port-channel must affect all the ports within the channel, but configuring an interface (port) only affects the particular interface not the port-channel.

How does EtherChannel works ?

EtherChannel is used to bundle multiple interface links into a single logical link. In a single EtherChannel we can add up to 8 interfaces.

  

What is the use of EtherChannel, why do i bundle multiple links into one?

If we have a fast Ethernet switch which has the speed of 100 Mbps per interface (port). Our workload and data stream is increasing day by day. Now what to do if 100 Mbps is not enough to forward our data stream? Simple, sell the fast Ethernet switch on eBay and get one brand new Cisco Gigabit EtherChannel switch. ;)

Replacing the Hardware is not always the best thing to do. What if the same issue happens to a guy who got Gigabit EtherChannel switch? To overcome this problem EtherChannel is used to bundle multiple fast Ethernet interface in to one.

In a fast Ethernet switch speed of an interface is up to 100 Mbps, if we bundle 8 interfaces in to one, we get the total speed of 800 Mbps. In Gigabit EtherChannel a bundle of 8 interfaces gives the speed up to 8 Gbps.

Now what if a single link in an EtherChannel goes down? Nothing happens, still the bundle works fine with the rest of the 7 links (800-100 = 700) which has the speed of 700 Mbps.

Spanning Tree Protocol (STP) considers the bundled EtherChannel has a single link, so link failure inside the bundle doesn’t affect the STP to recalculate the redundancy.

We can create EtherChannel for Layer2 interface and also for Layer3 interface. Configuring method is different. All the interfaces in an EtherChannel must be configured as either Layer 2 or Layer 3 interfaces. All interfaces in an EtherChannel must be in same speed.

How to configure EtherChannel ?

How to Configure HSRP v2 ?

There's no much difference between configuring HSRP v1 & HSRP v2. HSRP version 2 will not interoperate with HSRP version 1. HSRP v1 & 2 won't work in same interface. But we can configure v1 in one interface and v2 in another interface of the same router. Group number has been extended in version 2. version 1 supports (0 - 255) whereas, version 2 supports (0 - 4095)

New features in HSRP v2

• HSRP version 2 Group range has been extended 0 through 4095. 

• Version 1 timer values are advertised and learned in seconds, it doesn't support millisecond timers. In v2 millisecond timer values added an advantage.

• HSRP v 2 uses the new IP multicast address 224.0.0.102 to send hello packets instead of 224.0.0.2, which is used by version 1. 

• In v1 we can't identify the source of the hello packet, because router uses HSRP virtual MAC address as it's source address, which doesn't contain interface address. HSRP v2 includes a 6-bye identifier field which includes the MAC address of the local interface.

• MAC address range 0000.0C9F.F000 to 0000.0C9F.FFFF. 

• v2 cannot inter-operate with v1 because version 2 has a different packet format than v1.

Configuration Methods : 

 Step 1 : Router > enable

Step 2 : Router# configure terminal

Step3 : Router(config)#interface vlan100

Step4 : Router(config-if)# ip address 192.168.1.1 255.255.255.0

Step 5 : Router(config-if)# standby version 2    ( it shows we changed v1 to v2 )

Step 6 : Router(config-if)# standby 100 ip 192.168.1.100
( in HSRP v2 the range of group number is extended to 0 - 4095)

Step 7 : Router(config-if)# end