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Webcast-Catalyst9k
New Member

LACP Configuration with two links

Hi,

Does LACP provides load balcing & Redundancy together  on an ether-channel with two links?

I have two links to my access switches from distribution swith. Which etherchannel protocol (LACP/PAGP)will give me redundacy as well as load-balancing/bandwidth aggregation?

DS Switch:

Catalyst 4500‐X 24

Access Switch:

Catalyst 2960s

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4 REPLIES
Cisco Employee

LACP Configuration with two links

Hi Sambhab,

Both PAgP and LACP are only negotiation protocols that allow two devices to dynamically negotiate the creation of an EtherChannel. While using either of them is highly recommended, they do not influence how the EtherChannel works. The redundancy and load balancing is provided to you by the very way EtherChannel works itself.

In other words, you may use either LACP or PAgP (LACP is recommended as it is an open standard). EtherChannels negotiated by any of these two protocols will provide you with redundancy and load balancing.

Best regards,

Peter

Purple

LACP Configuration with two links

  While lacp or pagp aggregates the ports the  most bandwidth a given ip conversation will have is whatever links you are using. Say you have 4 1 gig links channeled together , the fastest a given ip conversation can go is 1 gig as a given conversation will go over one of those 4 links .   While the total traffic will be hashed across all 4 to "even" out the load .

New Member

LACP Configuration with two links

Thanks to all for the reply.

In my scenario, I am using lacp protocol  for etherchannel with two(2) links.Right now,It is giving me redundancy.

Also, I have configured load balance: src-dst-mac.

It will give me load balance or not.

Cisco Employee

LACP Configuration with two links

Hi Sambhab,

It will also give you load balancing - but as Glen has explained, the EtherChannel technology always puts a single conversation to a single link in the EtherChannel bundle. Therefore, you will load balance multiple conversations only. This is again a fundamental feature of EtherChannel technology, and neither LACP nor PAgP can influence this.

Personally, I suggest using the src-dst-ip or even src-dst-port if supported, as this will enable your device to load balance using IP addresses or even L4 transport ports which exhibit the highest variability in different conversations. The src-dst-mac is a usable setting but the src-dst-ip will give you the same, if not better, load spreading characteristics.

Best regards,

Peter

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