Implementing Spanning Implementing Spanning TreeTree

Module 3 - Part 4Module 3 - Part 4EtherchannelEtherchannel

Jane Brooke (Centennial College)Jane Brooke (Centennial College)mods by Emerson Hunt mods by Emerson Hunt

EtherChannelEtherChannel

About EtherChannelAbout EtherChannel Logical aggregation of bandwidthLogical aggregation of bandwidth Viewed as one logical portViewed as one logical port

by STP, trunking, access and for by STP, trunking, access and for administrationadministration

Bind 2 - 8 portsBind 2 - 8 ports Yields 1600Mbps (FastEther) or Yields 1600Mbps (FastEther) or

16Gbps(GigabitEther)16Gbps(GigabitEther)

Load balancing algorithm differs by platformLoad balancing algorithm differs by platform

Etherchannel BenefitsEtherchannel Benefits

Use all available bandwidth by logically Use all available bandwidth by logically “bundling” up to eight physical links“bundling” up to eight physical links

The logical Etherchannel can be managed The logical Etherchannel can be managed as a single unit called a as a single unit called a port channelport channel or or channel groupchannel group

Seen as one bySeen as one by Shutdown/no shutdownShutdown/no shutdown Sh spanning treeSh spanning tree Sh interface trunkingSh interface trunking

Etherchannel BenefitsEtherchannel Benefits

Load is balanced across physical linksLoad is balanced across physical links Although balancing algorithm is not necessarily Although balancing algorithm is not necessarily

optimaloptimal Under some circumstances balancing is unevenUnder some circumstances balancing is uneven

Remaining links continue to operate if a Remaining links continue to operate if a member of the etherchannel bundle failsmember of the etherchannel bundle fails Loss of a line in an etherchannel is not seen by Loss of a line in an etherchannel is not seen by

STASTA Failover time is only millisecondsFailover time is only milliseconds

Used Where?Used Where?

L2 as trunk between two switchesL2 as trunk between two switches L3 as connection between two routersL3 as connection between two routers Access linkAccess link

typically between switch and server with typically between switch and server with appropriate NICs (NIC "teaming")appropriate NICs (NIC "teaming")

Etherchannel and ServersEtherchannel and Servers

Multiple NICs can be installed in a server Multiple NICs can be installed in a server and a higher bandwidth aggregated link and a higher bandwidth aggregated link can be formed between the server and the can be formed between the server and the switchswitch

Known as ``nic teaming``Known as ``nic teaming`` May not be supported natively by the May not be supported natively by the

server OSserver OS Proper choice of the load balancing Proper choice of the load balancing

algorithm is important with NIC teamingalgorithm is important with NIC teaming

EtherChannel Dynamic Trunk EtherChannel Dynamic Trunk

Negotiation ProtocolsNegotiation Protocols PAgPPAgP Cisco proprietary Cisco proprietary Sends PAgP packets Sends PAgP packets

across link to negotiate across link to negotiate EtherChannelEtherChannel

LACPLACP IEEE standard 802.3adIEEE standard 802.3ad

Sends LACP packets across Sends LACP packets across link to bundle multiple ports link to bundle multiple ports into a single channelinto a single channel

Use in mixed switch Use in mixed switch environmentenvironment

EtherChannel Interface ModesEtherChannel Interface Modes ONON –– Forces EtherChannel ON without PAgP or Forces EtherChannel ON without PAgP or

LACP negotiation (not recommended)LACP negotiation (not recommended) PAgPPAgP

AutoAuto (default PAgP mode) (default PAgP mode)• interface enters passive negotiating state interface enters passive negotiating state • responds to PAgP packets received but doesn’t initiate PAgP responds to PAgP packets received but doesn’t initiate PAgP

negotiationnegotiation DesirableDesirable (PAgP mode) (PAgP mode)

• interface actively negotiates with other interfacesinterface actively negotiates with other interfaces• PAgP packets are exchangedPAgP packets are exchanged

LACPLACP PassivePassive (Default LACP mode) (Default LACP mode)

• port responds to LACP packets received, but it does not initiate port responds to LACP packets received, but it does not initiate LACP packet negotiation LACP packet negotiation

Active Active • port actively negotiates state with other ports by sending LACP port actively negotiates state with other ports by sending LACP

packets packets

The DefaultsThe Defaults

AutoAuto for PAgP and for PAgP and passivepassive for LACP for LACP Means that by default, links WILL NOT aggregate Means that by default, links WILL NOT aggregate

automaticallyautomatically Best practice is toBest practice is to

Explicitly set aggregation protocol using the Explicitly set aggregation protocol using the channel-protocolchannel-protocol command command

manually configure using the manually configure using the channel-groupchannel-group commandcommand

PAgP is the proprietary default link PAgP is the proprietary default link aggregation protocol on Cisco switchesaggregation protocol on Cisco switches

Use LACP for vendor neutralityUse LACP for vendor neutrality

PAgPPAgP

PAgP packets sent between Etherchannel PAgP packets sent between Etherchannel ports – negotiate forming channelports – negotiate forming channel

Etherchannel seen as single bridge port to Etherchannel seen as single bridge port to spanning treespanning tree Packets sent every 30 secondsPackets sent every 30 seconds Multicast out MAC 01-00-0C-CC-CC-CCMulticast out MAC 01-00-0C-CC-CC-CC Ensures all ports have same speed, duplex Ensures all ports have same speed, duplex

and VLAN infoand VLAN info

The RulesThe Rules

All links in a channel-group must be almost All links in a channel-group must be almost identicalidentical Speed and duplexSpeed and duplex Switch port mode (trunk or access)Switch port mode (trunk or access) If access, belong to same vlanIf access, belong to same vlan If trunk, same vlans allowedIf trunk, same vlans allowed

Each etherchannel must be assigned a Each etherchannel must be assigned a channel group number (1-64)channel group number (1-64)

Creates a Port-channel interface section in Creates a Port-channel interface section in running configrunning config

Guidelines for Configuring Guidelines for Configuring EtherChannelEtherChannel

Guidelines for Configuring Guidelines for Configuring EtherChannel (Cont.)EtherChannel (Cont.)

Interfaces in the same bundle can support varying port costs

About EtherChannel About EtherChannel Configuration CommandsConfiguration Commands

Configure PAgPConfigure PAgPinterface range blah blahinterface range blah blahchannel-protocol pagpchannel-protocol pagpchannel-group X mode autochannel-group X mode auto

Configure LACPConfigure LACPinterface range blah blahinterface range blah blahchannel-protocol lacpchannel-protocol lacpchannel-group X mode activechannel-group X mode active

VerifyVerifyshow interfaces fastethernet 0/1 etherchannelshow interfaces fastethernet 0/1 etherchannelshow etherchannel 1 port-channelshow etherchannel 1 port-channelshow etherchannel 1 summaryshow etherchannel 1 summary

Configuring L2 EtherChannelConfiguring L2 EtherChannel

Switch(config-if-range)#channel-protocol {pagp | lacp}Switch(config-if-range)#channel-protocol {pagp | lacp}

• Create the port-channel interface and place the interfaces as members

Switch(config)#interface range interface slot/port - portSwitch(config)#interface range interface slot/port - port

• Specify the interfaces to configure in the bundle

Switch(config-if-range)#channel-group number mode {auto | desirable | active | passive | on}Switch(config-if-range)#channel-group number mode {auto | desirable | active | passive | on}

• Specify the channel protocol either pagp OR lacp

PAgP is default on Cisco switches.

Verifying EtherChannelVerifying EtherChannelSwitch#show running-config interface port-channel num Switch#show running-config interface port-channel num

• Displays port-channel information Switch#show run interface port-channel 1 Building configuration...

Current configuration : 66 bytes!interface Port-channel1 switchport mode dynamic desirableend

Switch#show running-config interface interface x/y Switch#show running-config interface interface x/y

• Displays interface informationSwitch#show run interface gig 0/9Building configuration...

Current configuration : 127 bytes!interface GigabitEthernet 0/9 switchport mode dynamic desirable channel-group 2 mode desirable channel-protocol pagpend

Verifying EtherChannel (Cont.)Verifying EtherChannel (Cont.)Switch#show interfaces gigabitethernet 0/9 etherchannelPort state = Up Mstr In-BndlChannel group = 1 Mode = Desirable-Sl Gcchange = 0Port-channel = Po2 GC = 0x00020001 Pseudo port-channel = Po1Port index = 0 Load = 0x00

Flags: S - Device is sending Slow hello. C - Device is in Consistent state. A - Device is in Auto mode. P - Device learns on physical port. d - PAgP is down.Timers: H - Hello timer is running. Q - Quit timer is running. S - Switching timer is running. I - Interface timer is running.

Local information: Hello Partner PAgP Learning GroupPort Flags State Timers Interval Count Priority Method IfindexGi0/9 SC U6/S7 H 30s 1 128 Any 15

Partner's information:

Partner Partner Partner Partner GroupPort Name Device ID Port Age Flags Cap.Gi0/9 DSW122 0005.313e.4780 Gi0/9 18s SC 20001

Age of the port in the current state: 00d:20h:00m:49s

Load BalancingLoad Balancing

Etherchannel provides a choice of Etherchannel provides a choice of algorithms to determine which bundle algorithms to determine which bundle member will carry a given framemember will carry a given frame

Various load-balancing methods are Various load-balancing methods are available (choices are platform dependant)available (choices are platform dependant)

The default method may lead to some The default method may lead to some members being more heavily utilized than members being more heavily utilized than othersothers

ExampleExample

Suppose we have an Etherchannel Suppose we have an Etherchannel connecting a switch to a serverconnecting a switch to a server

One type of algorithm depends solely on One type of algorithm depends solely on destination mac addressdestination mac address All frames destined for the same mac address All frames destined for the same mac address

will use the same wirewill use the same wire Therefore virtually all server bound frames will Therefore virtually all server bound frames will

use just one wire in the etherchanneluse just one wire in the etherchannel

Balancing MethodsBalancing Methods

src-ipsrc-ip dst-ipdst-ip src-dst-ipsrc-dst-ip src-macsrc-mac dest-macdest-mac

src-dst-macsrc-dst-mac src-portsrc-port dst-portdst-port src-dst-portsrc-dst-port

Available Methods & which is the default

vary by platform

Configuring EtherChannel Load Configuring EtherChannel Load BalancingBalancing

Switch#show etherchannel load-balance Source XOR Destination IP address

Switch(config)#port-channel load-balance typeSwitch(config)#port-channel load-balance type

• Note that this is a global command• I.e. method cannot be configured on a per-channel basis

• To see the current load balancing method, use the following:

NotesNotes

the default method will usually result in a the default method will usually result in a fair balancingfair balancing

the following command will give some the following command will give some sense of the fairness of the load balancing sense of the fairness of the load balancing algorithmalgorithm show etherchannel port-channel Xshow etherchannel port-channel X

Look for the "load" value on each channelLook for the "load" value on each channelThey should be similarThey should be similar

ResourcesResources

http://networkers-online.com/blog/2008/07/etherchannel-load-balancing-case-study/

Personal NotesPersonal Notes

Etherchannel works (sort of) in Packet TracerEtherchannel works (sort of) in Packet Tracer I have had PT 5.1 crash when playing with I have had PT 5.1 crash when playing with

multiple Etherchannelsmultiple Etherchannels Packet tracer definitely does not accurately Packet tracer definitely does not accurately

simulate show command output where port simulate show command output where port channels are involvedchannels are involved

However, etherchannel also seems a bit However, etherchannel also seems a bit flakey on our equipmentflakey on our equipment Lab suggests "flapping" the interfaces if the Lab suggests "flapping" the interfaces if the

Etherchannel does not come upEtherchannel does not come up