Etherchannel load balancing?

G'day all,

I have a question about the logic used by Etherchannel load balancing.

I have this exert from the CCNP book:

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Traffic in an EtherChannel is distributed across the individual bundled
links in a deterministic
fashion; however, the load is not necessarily balanced equally across all
the links. Instead, frames
are forwarded on a specific link as a result of a hashing algorithm. The
algorithm can use source IP
address, destination IP address, or a combination of source and destination
IP addresses, source
and destination MAC addresses, or TCP/UDP port numbers. The hash algorithm
computes a binary
pattern that selects a link number in the bundle to carry each frame.

If only one address or port number is hashed, a switch forwards each frame
by using one or more
low-order bits of the hash value as an index into the bundled links. If two
addresses or port
numbers are hashed, a switch performs an exclusive-OR (XOR) operation on one
or more loworder
bits of the addresses or TCP/UDP port numbers as an index into the bundled
links.

For example, an EtherChannel consisting of two links bundled together
requires a 1-bit index. If
the index is 0, link 0 is selected; if the index is 1, link 1 is used.
Either the lowest-order address bit
or the XOR of the last bit of the addresses in the frame is used as the
index. A four-link bundle
uses a hash of the last 2 bits.
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Now things Im not sure about:
In an etherchannel running a dot1q trunk the only options I can use are
src-mac and dst-mac correct? Or is there a better way to get more throughput
over etherchannels running dot1q trunks?

Also am I right to say that the logic isn't that great? It just comes down
to a 1bit even or odd number based on either the source or destination mac
of the flow depending on what method I have selected?

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Received on Fri May 29 2009 - 16:33:32 ART