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Cisco Bug: CSCuq86217 - M1XL SPAN Destination port-channel does not load balance

Last Modified

Aug 12, 2015

Products (8)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 4-Slot Switch
  • Cisco Nexus 7700 6-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch
  • Cisco Nexus 7700 18-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch
  • Cisco Nexus 7700 10-Slot Switch

Known Affected Releases

6.1(3) 6.2(2a) 6.2(8a)

Description (partial)

Symptom:
On N7K when using interfaces from a M1XL linecard, SPAN traffic will only traverse one port-channel member.  See example setup below:
N7K# show monitor session 1 
   session 1
---------------
type              : local
state             : up
source intf       : 
    rx            : Eth4/1        Eth4/2        
    tx            : Eth4/1        Eth4/2        
    both          : Eth4/1        Eth4/2        
source VLANs      : 
    rx            : 
    tx            : 
    both          : 
filter VLANs      : filter not specified
destination ports : Po100         

N7K-7010.66# sho port-c traffic 
NOTE: Clear the port-channel member counters to get accurate statistics

ChanId      Port Rx-Ucst Tx-Ucst Rx-Mcst Tx-Mcst Rx-Bcst Tx-Bcst
------ --------- ------- ------- ------- ------- ------- -------
   100    Eth4/3    0.0% 100.00%  50.00% 100.00%    0.0%    0.0%    <----- 100% TX
   100    Eth4/4    0.0%    0.0%  50.00%    0.0%    0.0%    0.0%    <----- No TX
   
According to the documentation below, M1XL port-channels can be used as SPAN destinations and should load balance.

"If a port channel is the SPAN destination interface for SPAN traffic that is sourced from a Cisco Nexus 7000 M1 Series module, only a single member interface will receive copied source packets. The same limitation does not apply to SPAN traffic sourced from all other Cisco Nexus series modules, including the Cisco Nexus 7000 M1-XL Series modules."
Source: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/6_x/nx-os/system_management/configuration/guide/sm_nx_os_cg/sm_14span.html#pgfId-1312959

Conditions:
Local SPAN session on N7K using M1XL linecard.
Version 6.x
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