[c-nsp] Issue with port-channel hashing

Mack McBride mack.mcbride at viawest.com
Fri Jul 22 18:53:23 EDT 2016

With some traffic patterns there isn't much you can do.
If there are very few source and destination addresses then you may not be able to
Distribute the traffic.  Especially for long lived flows.

Try 'port-channel load-balance src-dst-mixed-ip-port' if you are on code that supports it.
Also ensure you have 'port-channel load-balance per-module'.
You already found the adaptive knob.
Adaptive is more difficult to troubleshoot when there are issues.

You may also want to set 'mls ip cef load-sharing full'.

Mack McBride | Senior Network Architect | ViaWest, Inc.
O: 720.891.2502 | C: 303.720.2711 | mack.mcbride at viawest.com | www.viawest.com

-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of james list
Sent: Friday, July 22, 2016 1:45 AM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Issue with port-channel hashing

Dear experts,

I need help.

On my C6500 sup720 (12.2(33)SXI5) I’ve a port channel 4 x 1Gbs with 1 Gbs full and hashing fixed.

On the port-channel I’m trunking with few L2 vlans and on top of one of those I’ve L3 (with OSPF).

Since hashing is fixed all the traffic that 6500 Asic has decided to send on that link is experiencing problems.

My questions:

1)      Which is the faster and safer way to detect the “guilty” (src/des
tip) ? I see accounting seems not working

2)      What if I would change hashing from fixed to adaptive ? any detail
on that ? I'm not able to find how it works in detail on cisco.com

An help is appreciated,


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