load balancing on Etherchannel

[Vikram_Anumukonda_2]

     on a l2 switch what will happen if i leave default load-balancing algorithm on a port-channel  ( which I guess

is src-ip address/dst-ip address ) ?

[smehrnia · Accepted solution]

Hi Vikram

it is src-MAC and dst-MAC, with source-MAC address forwarding, when packets are forwarded to an EtherChannel, the packets are distributed across the ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide load balancing, packets from different hosts use different ports in the channel, but packets from the same host use the same port in the channel.

and with dst-MAC same thing happenes but with taking dst-Mac into account.

you may want to know this load balancing behaviour is different for different platforms.

plz Rate if it helped.

Soroush.

[Vikram_Anumukonda_2]

Hi Soroush, When should I use src-dst-ip loadbalancing, is this dependent on the IOS version ?

I am trying to figure out how the switch falls back  to src-dst-mac loadbalancing when  src-dst-ip loadbalancing is configured  on it .

As an example i am running the below version

Catalyst 4500 L3 Switch Software (cat4500e-IPBASEK9-M), Version 12.2(53)SG1, RELEASE SOFTWARE (fc1)

and it supports the below load-balancing methods

show etherchannel load-balance

EtherChannel Load-Balancing Configuration:

        src-dst-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:

Non-IP: Source XOR Destination MAC address

  IPv4: Source XOR Destination IP address

  IPv6: Source XOR Destination IP address

Does this mean that the swictch looks into the IP header for src & dst ip's before loadbalancing ?

[smehrnia · Accepted solution]

Hi Vikram,

being able to use Src-dst-ip load balancing depends on the chasis you are using, some Switches are capable of doing Layer 3 load balancing (IP) some other only allow Layer 2 (Mac address).

here is a helpfull Link that explains etherchannel load balancing with regards to the switch type you have, and an informative table that i hope you will find useful:

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml#matrix

Hope it Helps,

Soroush.

[Vikram_Anumukonda_2]

Thank you

[smehrnia]

this shows your current configuration is based on src-dst IP load balancing for IPv4 and IPv6. for other non-ip protocols it is obvious since they dont have an ip address, switch will use Mac address instead.

Yes, switch looks into ip header (source - destination address) and then decide on which link it forwards the packet.

Hope it Helps,

Soroush.