Configuring Port Channels by Link Aggregation

C H A P T E R 6

This chapter describes how to use the Link Aggregation feature to configure port-channels via the CLI and the Graphical User Interface.

This chapter contains the following topics:

Section , Using the Link Aggregation Feature

Section , Configuring Link Aggregation via CLI

Section , Configuring Link Aggregation via Web Interface

Using the Link Aggregation Feature

The Link Aggregation (LAG) feature allows the switch to treat multiple physical links between two end-points as a single logical link called a port-channel. All of the physical links in a given port-channel must operate in full-duplex mode at the same speed.

You can use the feature to directly connect two switches when the traffic between them requires high bandwidth and reliability, or to provide a higher bandwidth connection to a public network.

You can configure the port-channels as either dynamic or static. Dynamic configuration uses the IEEE 802.3ad standard, which provides for the periodic exchanges of LACPDUs. Static configuration is used when connecting the switch to an external switch that does not support the exchange of LACPDUs.

The feature offers the following benefits:

Increased reliability and availability -- if one of the physical links in the port-channel goes down, traffic is dynamically and transparently reassigned to one of the other physical links.

Increased bandwidth -- the aggregated physical links deliver higher bandwidth than each individual link.

Incremental increase in bandwidth -- A physical upgrade could produce a 10-times increase in bandwidth; LAG produces a two- or five-times increase, useful if only a small increase is needed.

Management functions treat a port-channel as if it were a single physical port.

You can include a port-channel in a VLAN. You can configure more than one port-channel for a given switch.

Configuring Link Aggregation via CLI

The following LAG Port Channel Example Network Diagram shows an example of configuring the software to support Link Aggregation (LAG) to a server and to a Layer 3 switch.

FIGURE 6-1 LAG Port Channel Example Network Diagram

CLI Example 1: Create Two Port Channels

CODE EXAMPLE 6-1 Creating Two Port Channels
(DTI SWITCH) #config (DTI SWITCH) (Config)#port-channel lag_10 (DTI SWITCH) (Config)#port-channel lag_20 (DTI SWITCH) (Config)#exit

Use the show port-channel all command to show the logical interface ids you will use to identify the port-channels in subsequent commands. Assume that lag_10 is assigned id 1/1 and lag_20 is assigned id 1/2.

CODE EXAMPLE 6-2 Showing Port Channels
(DTI SWITCH) #show port-channel all Port- Link Log. Channel Adm. Trap STP Mbr Port Port Intf Name Link Mode Mode Mode Type Ports Speed Active ------ ------------- ----- ---- ---- ------ ------- ------ --------- ------ 1/1 lag_10 Down En. En. Dis. Dynamic 1/2 lag_20 Down En. En. Dis. Dynamic

CODE EXAMPLE 6-2 Showing Port Channels

(DTI SWITCH) #show port-channel all
 
            Port-               Link
Log.       Channel         Adm. Trap  STP           Mbr      Port    Port
Intf        Name     Link  Mode Mode  Mode   Type   Ports    Speed   Active
------ ------------- ----- ---- ---- ------ ------- ------ --------- ------ 
1/1	lag_10      Down   En.  En.  Dis.  Dynamic
1/2	lag_20      Down   En.  En.  Dis.  Dynamic

CLI Example 2: Add Physical Ports to the Port Channels

CODE EXAMPLE 6-3 Adding Ports to the Port Channels
(DTI SWITCH) #config (DTI SWITCH) (Config)#interface 0/2 (DTI SWITCH) (Interface 0/2)#addport 1/1 (DTI SWITCH) (Interface 0/2)#exit (DTI SWITCH) (Config)#interface 0/3 (DTI SWITCH) (Interface 0/3)#addport 1/1 (DTI SWITCH) (Interface 0/3)#exit (DTI SWITCH) (Config)#exit (DTI SWITCH) #config (DTI SWITCH) (Config)#interface 0/8 (DTI SWITCH) (Interface 0/8)#addport 1/2 (DTI SWITCH) (Interface 0/8)#exit (DTI SWITCH) (Config)#interface 0/9 (DTI SWITCH) (Interface 0/9)#addport 1/2 (DTI SWITCH) (Interface 0/9)#exit (DTI SWITCH) (Config)#exit

CODE EXAMPLE 6-3 Adding Ports to the Port Channels

(DTI SWITCH) #config
(DTI SWITCH) (Config)#interface 0/2
(DTI SWITCH) (Interface 0/2)#addport 1/1
(DTI SWITCH) (Interface 0/2)#exit
(DTI SWITCH) (Config)#interface 0/3
(DTI SWITCH) (Interface 0/3)#addport 1/1
(DTI SWITCH) (Interface 0/3)#exit
(DTI SWITCH) (Config)#exit
 
(DTI SWITCH) #config
(DTI SWITCH) (Config)#interface 0/8
(DTI SWITCH) (Interface 0/8)#addport 1/2
(DTI SWITCH) (Interface 0/8)#exit
(DTI SWITCH) (Config)#interface 0/9
(DTI SWITCH) (Interface 0/9)#addport 1/2
(DTI SWITCH) (Interface 0/9)#exit
(DTI SWITCH) (Config)#exit

CLI Example 3: Enable Both Port Channels

By default, the system enables link trap notification.

CODE EXAMPLE 6-4 Enabling Both Port Channels
(DTI SWITCH) #config (DTI SWITCH) (Config)#port-channel adminmode all (DTI SWITCH) (Config)#exit

At this point, the LAGs could be added to the default management VLAN.

Configuring Link Aggregation via Web Interface

To perform the same configuration as described in the previous CLI sections, use: Switching --> Link Aggregation --> Configuration on the Web interface.

To create the port-channels, specify port participation and enable Link Aggregation (LAG) support on the switch.