Port-Channels on N2K Not Load Balancing

[marc.russo]

I have a dual-homed fabric (Nexus 2248 dual attached to two Nexus 5020's via vPC).  On this Nexus 2248 is a server that has a four port LACP etherchannel.  The ports do not appear to be load balancing correctly.  The output below shows the four ports in use and it clearly shows port e138/1/10 as getting the most use.  When I use the "show port-channel load-balance forwarding-path..." command on either of the vPC switches for various source and destination IP's that use this link, it shows them correctly load-balancing across the four ports.  But we do not see this when looking at stats on both the server side and the switch side.  Any ideas what I'm doing wrong?

dc5020-3g# sh int e138/1/10,e138/1/12,e138/1/14,e138/1/16 | i seconds

  30 seconds input rate 552 bits/sec, 69 bytes/sec, 0 packets/sec

  30 seconds output rate 130120 bits/sec, 16265 bytes/sec, 161 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

  30 seconds input rate 40 bits/sec, 5 bytes/sec, 0 packets/sec

  30 seconds output rate 1056 bits/sec, 132 bytes/sec, 1 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

  30 seconds input rate 32 bits/sec, 4 bytes/sec, 0 packets/sec

  30 seconds output rate 1096 bits/sec, 137 bytes/sec, 1 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

  30 seconds input rate 104 bits/sec, 13 bytes/sec, 0 packets/sec

  30 seconds output rate 1440 bits/sec, 180 bytes/sec, 1 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

**************** Config info below.  This is a vPC pair and the port configs are identical on both switches so I'm only showing the configs for one switch to keep it simple.

dc5020-3g# sh port-channel load-balance

Port Channel Load-Balancing Configuration:

System: source-dest-ip

Port Channel Load-Balancing Addresses Used Per-Protocol:

Non-IP: source-dest-mac

IP: source-dest-ip source-dest-mac

dc5020-3g# sh run int e138/1/10

!Command: show running-config interface Ethernet138/1/10

!Time: Thu Sep  6 16:09:56 2012

version 5.0(3)N2(1)

interface Ethernet138/1/10  (ports 12, 14 and 16 are the other ports in the port-channel and are configured the same)

  description nbdisk-1

  switchport mode trunk

  switchport trunk allowed vlan 4,12,14,21,77,114,128,242,246,277,1020,1200

  channel-group 1305 mode active

dc5020-3g# sh run int po1305

!Command: show running-config interface port-channel1305

!Time: Thu Sep  6 16:10:02 2012

version 5.0(3)N2(1)

interface port-channel1305

  description nbdisk-1

  switchport mode trunk

  switchport trunk allowed vlan 4,12,14,21,77,114,128,242,246,277,1020,1200

dc5020-3g#     

[Reza Sharifi]

You only have one server connecting to the 2248s? if so, than that is only one source.  All traffic would use only a single link. If you have 2 servers or more that the po should be using multiple physical ports.

HTH

[sajid_m123]

Please note that when server is sending traffic then server would use its algorithm for LB ( outgoing from server to destination in this case) and when switch is sending traffic back to server it would use source-dest-ip criteria.

If you ping multiple destinations from the same source, you may notice atleast returning traffic through differnt NICs.

Thanks!

[marc.russo]

So a little more information...

Got more details from the server folks yesterday.  The stats I posted above are not a true representation as the port-channel was mostly idle at that time.  When it is active the server guys see outbound traffic from the server (switch inbound) as being pretty well balanced.  Now this is handled by the server's load balancing algorithm.  What they also see is the inbound traffic to the server only returning on one port...which is the switch outbound traffic and thus handled by the switch load balancing algorithm  (src-dest-ip, src-dest-mac).  So I am assuming that for some reason the switch is not load balancing correctly.  I did confirm that the servers is virtual and has multiple IP's.  Regardless of which IP is communicating, only one port seems to be sending the return traffic to the server.  Is my load balancing algorithm correct for this setup?