3750x stack - changing etherchannel load balance configuration

[jkes]

Hello All,

I am installing a several new Cisco VM servers. The VM hosts are losing connectivity when we apply the etherchannel config in the core stack.  VMware has stated that the etherchannel load balance needs to be src-dst-ip in order for the etherchannel to work. 

However, my current stack has 2 etherchannels configured to other switches through out the bldg in network closets.  The current load balance configuration is src-mac.

My question....when I make the change to src-dst-ip, will my network connectivity go down?  I saw there was an older article on this that doesnt provide an answer just a work around.  Here is the article.  https://supportforums.cisco.com/message/560889#560889

Does the shut, no shut command fix the issue if I apply the change?  I will be applying this on a "live network" with both voice and data traffic being handled in the core 3750x stack.  I'm just a little concerned before I apply.....just need to verify before I apply.

Thanks,

Jay               

[Arumugam Muthaiah · Accepted solution]

Hi Jay,

The default frame-distribution method for etherchannel on the 3750 platform is to base the decision on the source-MAC address. If you change the settings, it affects all channels

Example:
3750_Switch#show etherchannel load-balance
EtherChannel Load-Balancing Operational State (src-mac):
Non-IP: Source MAC address
IPv4: Source MAC address
IPv6: Source IP address

3750_Switch#conf t
3750_Switch(config)#
3750_Switch(config)#port-channel load-balance src-dst-ip

3750_Switch#show etherchannel load-balance
EtherChannel Load-Balancing Operational State (src-dst-ip):
Non-IP: Source XOR Destination MAC address
IPv4: Source XOR Destination IP address
IPv6: Source XOR Destination IP address
3750_Switch#

Due to the implementation of the channel hashing, modifying the hashing algorithm will not negatively impact the performance of the switch, nor the processing time for individual frames.

The channel hashing is done in hardware on all these platforms, and there is no performance impact to the switch incurred by modifying the frame distribution method. It is of course important to choose the frame distribution method which most closely correlates with your traffic pattern to ensure that traffic is appropriately distributed.

Refer:

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

Regards,

Aru

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