Etherchannel Load Balance MAC/IP Adr. algorithm

Unanswered Question
Aug 12th, 2008
User Badges:

Hello,

on a Cisco Etherchannel or LACP Channel, with configured src-dst-mac Balancing, wich algorithm use Cisco IOS for the Port foward desicion based on Source und Destianion MAC Adr. or Source and Dest. IP Adr (for a src-dst-IP Balancing)?


Thanks?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Giuseppe Larosa Wed, 08/13/2008 - 00:03
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Juergen,


it is a bit level EXOR of last significant bits of source and destination address


the result of the EXOR of the last m bits is used to point to the member link of the bundle


if using two links is only the exor of the last bit (less significant bit)

if using four links is the exor of the last two bits (index 00 to 11)


if the number of links is odd they use one more bit

example : 3 links it uses the last three digits here 3/8, 3/8 2/8 are mapped to the three links


Hope to help

Giuseppe

jkunzbva8 Wed, 08/13/2008 - 00:14
User Badges:

Hello Guiseppe,


thanks for the answer!


I have tested a 2 Channel Link with the 2 Client Mac-Adr., the less significant bit: Client 1: ....3F and Client 2: ....A7, Dest Mac is ....24.

In this case Client 1 traffic should be forwarded on Channel-Port 1 and Client 1 traffic should be forwarded on Channel-Port 2!

But only Channel-Port 1 is used!

We find out that on a 2 Link channel, not only the less significant bit is used for the forwarding desicion?!?

Giuseppe Larosa Wed, 08/13/2008 - 05:32
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Juergen,


binary digit EXOR of last bit


3F => 0011 1111

A7 => 1010 0111


last bit client 1 : 1

last bit client 2: 1


dest mac 24 => 0010 0100


last bit dest = 0


0 exor 1 in both cases so it is right what you see only one link is used in this case


Hope to help

Giuseppe


Actions

This Discussion