RE: L3 Port Channel Question.

To add to Marko's point: some platforms give the ability to load balance based on layer 4 port numbers and in some scenarios using them would give better load distribution rather than using the other method. In my opinion it would all boil down to the network requirements. One more thing that I could think of where using port channel would be a benefit is QOS.

Also, regarding the hash values each platform has a separate way of calculating it like 6500 does not use the vlan number in computing hash while Nexus has the support for the same. I am not sure about the routers though.

/Ruchir

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Marko Milivojevic
Sent: Monday, January 04, 2010 11:30 PM
To: Radioactive Frog
Cc: Poplawski, James; Cisco certification
Subject: Re: L3 Port Channel Question.

On Mon, Jan 4, 2010 at 18:43, Radioactive Frog <pbhatkoti_at_gmail.com> wrote:
> Good question!
>
> AFAIK the tie breaker for chosing OSPF over a L3 port channeling would be
> "OSPF provides MULTIPLE path load balancing".
> Also checks multiple other network related parameters (latency bandwidth
> etc). With L3 port channeling we can't enforce based on bandwidth/load,
> etc).

Sorry but you are not correct here. OSPF does not take anything other
than cost to the destination as the basis for load sharing. If more
than one link shares the the same cost to the destination, it will be
load shared. Where packet is sent to depends on the hash the CEF uses.
I'm sort of tip toeing around defining the hash, because I'm not 100%
sure what it consists of by default...

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Marko Milivojevic - CCIE #18427
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