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ProCurve LAG load balancing methods.

 
akopylov
Occasional Advisor

ProCurve LAG load balancing methods.

Hello there.

I got 2 ProCurve 6120XG switches (hp c7000 onboard). I`m currently reading user guide http://h10032.www1.hp.com/ctg/Manual/c01868095.pdf and I am confused about load balancing methods within a trunk group.

I see there are few methods:

 

ProCurve 6120XG Switch Right(config)# trunk-load-balance
 L2-based              Load balance based on Layer 2 information.
 L3-based              Load balance based on Layer 3 information (if present)
                       or Layer 2 information; this is the default.
 L4-based              Load balance based on Layer 4 information (if present),
                       or Layer 3 (if present), or Layer 2.
 source-mac-based      Load balance based on source MAC address information.

And this is quote from the user guide (about L3 method):

 

When an IP address is available, the calculation includes the last five bits of the IP source address and IP destination address, otherwise the MAC addresses are used.

How can it be? I mean IP address is always available, but mac address is not, e.g. if the destination host resides behind the gateway. In this case the source knows the destination IP, but the destination MAC address is available only to gateway. So the method should work like "if the mac address available - use it, if not - use IP address", isn`t it?

1 REPLY 1
16again
Respected Contributor

Re: ProCurve LAG load balancing methods.

Ethernet frames always contain ethernet source/dest mac addresses.
But not all ethernet frames contain IPv4 addresses:  Bot only relics from the past like IPX adn BETBUI, but als loopdetection, spanning tree....and ipv6