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Port Channeling – a low cost way of increasing bandwidth and redundancy utilizing existing network infrastructure, such as turning four 1 Gigabit connections into one 4 Gigabit connection (if one link is lost the channel stays up with 3Gig functionality).

Network infrastructure often times can be the largest cost when engineering and maintaining a datacenter environment. Additionally the lifespan of this gear is typically finite and predictable as business growth and new technologies drive the organization to higher levels of availability, redundancy and bandwidth. The migration path to new network equipment is seldom a straight line, with budget driving much of the decisions; this being the case, it often becomes the network engineer’s responsibility to find a way to stretch existing equipment to its limits until it becomes possible to roll out new gear.

Naming conventions:

Etherchannel (Cisco’s proprietary channel protocol)

• aka Port Aggregation Protocol (PAGP) used between Cisco equipment.
• Fast EtherChannel (FEC) or Gigabit EtherChannel (GEC) are terms often used to describe the speed used to form the Etherchannel

Link Aggregation Control Protocol (LACP)

• vendor neutral, used between unlike equipment including servers and Load Balancers, etc.

Things to consider before creating a Port Channel:

• Can use up to 8 ports which must exist on the on the same blade of a modular switch, such as a Cisco 6500.
• All ports must be of the same speed and media type

Configuration example:

Combining four 1gig uplinks to one 4Gig PortChannel:

Wiring:

4948  module1 port 45 <connected to> Cisco 6500 Module 6 port 1

4948 gi1/46 <-> 6500 gi6/2

4948 gi1/47 <-> 6500 gi6/3

4948 gi1/48 <-> 6500 gi6/4

On Cisco 4948 switch:

!—note using range command here to propagate configuration to ports 45 – 48

My_4948_swich(config)# interface range gi1/45 – 48

My_4948_swich(config-if)# description UPLINKTO6500

My_4948_swich(config-if)# no ip address

My_4948_swich(config-if)# switchport

My_4948_swich(config-if)# switchport mode access

!—note the desireable setting here will allow for one link to drop while the others stay up

My_4948_swich(config-if)# channel-group 1 mode desirable

My_4948_swich(config-if)# no shutdown

!—PortChannel interface creation

My_4948_swich(config)# interface Po 1

My_4948_swich(config-if)# description UPLINKTO6500

My_4948_swich(config-if)# switchport

My_4948_swich(config-if)# switchport mode access

My_4948_swich(config-if)# no shutdown

!—Verify results

!–<will display etherchannels, associated interfaces and status>

show etherchannel summary

!–<will display PortChannel status, statistics including capacity>

show interface Po 1

On 6500 catalyst switch:

!Gigabit interface configuration

My_6500_swich(config)# interface range gi6/1 – 4

My_6500_swich(config-if)# description DOWNLINKTO4948

My_6500_swich(config-if)# no ip address

My_6500_swich(config-if)# switchport

My_6500_swich(config-if)# switchport mode access

My_6500_swich(config-if)# channel-group 101 mode desirable

My_6500_swich(config-if)# no shutdown

!–PortChannel interface creation

My_6500_swich(config)# interface Po 101

My_6500_swich(config-if)# description DOWNLINKTO4948

My_6500_swich(config-if)# switchport

My_6500_swich(config-if)# switchport mode access

My_6500_swich(config-if)# no shutdown

!—Verify results

!–<will display etherchannels, associated interfaces and status>

show etherchannel summary

!–<will display PortChannel status, statistics including capacity>

show interface Po 101

PortChannelling is a nice built in feature to utilize allowing you to provide increased bandwidth and fault tolerance for the cost of a couple unused interfaces, provided you have these to spare of course!

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