EtherChannel Configuration with Odd Number of Ports – IEEE 802.1AX Guide

etherchannelieee-802.1ax

Is the requirement of 2ⁿ number of ports for EtherChannel a critical requirement or just a recommendation to ensure, perhaps, an even load balancing?

Particularly, if we setup an EtherChannel group with 8 ports but one of them went down. Would the remaining 7 ports still be functional but with uneven load balance, or would 3 ports be forced into standalone to ensure a power of two group?

Is it dealt with similarly for both PAgP and LACP?

Best Answer

The power of 2 requirement varies per vendor/hardware/software. Cisco had (has) a pretty bad stigma against them with a lot of the earlier catalyst switches capable of 10G. The problem comes with how the software hashes (or "balances") data over the multiple ports in the port-channel (this is agnostic of PAgP or LACP).

This post does an excellent job of simplifying the problem in finer detail. This is less relevant today with hardware/software improvements, but again, it varies - so just check your hardware requirements and make sure you're not buying older hardware that falls victim to this problem.

http://www.packetmischief.ca/2012/07/24/doing-etherchannel-over-3-5-6-and-7-link-bundles/

Related Solutions

Cisco – Etherchannel connections between Cisco and Nortel switches

Look at this link and scroll about half way down.

http://forums.networkinfrastructure.info/nortel-ethernet-switching/ers-8300-and-lacp-with-hp-blade-servers/

UPDATE: Fixed - Here's how you get LACP to work with the 8300.

The configuration is simple, for a base line.

Configure your ports and vlans as you would normally (for multiple vlans enable tagging on the port level)

config ethernet 1/1-1/2,2/1-2/2 perform-tagging enable
config ethernet 1/1-1/2,2/1-2/2 lacp key 10
config ethernet 1/1-1/2,2/1-2/2 lacp aggregate true
config ehternet 1/1-1/2,2/1-2/2 lacp enable

config vlan 2 create byport 1
config vlan 2 ports add 1/1-1/2,2/1-2/2 member portmember

Configure your mlt group

config mlt 5 create
config mlt 5 lacp key 10
config mlt 5 lacp enable

Can we combine different kind of interface in Etherchannel

Packet tracer is a simulation for Network academy not a IOS emulator (like say GNS3) if there is a conflict between the doc and packet tracer, packet tracer looses. If you read further in the documentation a LOT of things have to match for an etherchannel bundle can form and link speed is one of them.

A corner case MAY be etherchannel autonegotated ports that end up at different speeds, but etherchannel will react to dynamic changes and drop ports out of the etherchannel so I don't think that will work.

Nor do you want it to as with non nexus hardware the load balance is power of 2 (3 ports will result in 1 of them getting 50% of the traffic) and there is no variable load balancing (a gig port gets 2x traffic of say 5 100 meg ports)

Best Answer

Related Solutions

Cisco – Etherchannel connections between Cisco and Nortel switches

Can we combine different kind of interface in Etherchannel

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