Symptom

A Nexus 9000 series switch configured with sFlow data sources is not able to administratively bring SPAN sessions online. This is expected behavior and is a documented limitation under the "Guidelines and Limitations for sFlow" heading of the "Configuring sFlow" chapter in the Cisco Nexus 9000 Series NX-OS System Management Configuration Guide document: "If at least one sFlow data source is configured, the SPAN sessions cannot be brought up." This is demonstrated below: switch# show run sflow feature sflow sflow data-source interface port-channel1 switch# show run monitor monitor session 1 source interface port-channel10 tx destination interface sup-eth0 switch# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 down Session admin shut switch# configure terminal Enter configuration commands, one per line. End with CNTL/Z. switch(config)# monitor session 1 switch(config-monitor)# no shut switch(config-monitor)# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 down Session admin shut However, if one removes all sFlow data sources from the switch's configuration and attempts to administratively bring the SPAN session up, the SPAN session will remain in a down state. switch# configure terminal Enter configuration commands, one per line. End with CNTL/Z. switch(config)# no sflow data-source interface port-channel1 switch(config)# end switch# show run sflow feature sflow switch# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 down Session admin shut switch# configure terminal Enter configuration commands, one per line. End with CNTL/Z. switch(config)# monitor session 1 switch(config-monitor)# no shut switch(config-monitor)# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 down Session admin shut

Conditions

This issue is observed when one initially attempted to bring a SPAN session up while a Nexus 9000 series switch was configured with at least one sFlow data source. After the sFlow data sources were removed, the SPAN session can still not be brought up.

Workaround

You can work around this issue by administratively shutting down the SPAN session (even though it's technically already administratively shut down), then attempting to bring it back up. An example of this is shown below: switch# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 down Session admin shut switch# show run monitor monitor session 1 source interface port-channel10 tx destination interface sup-eth0 switch# configure terminal Enter configuration commands, one per line. End with CNTL/Z. switch(config)# monitor session 1 switch(config-monitor)# shut switch(config-monitor)# no shut switch(config-monitor)# show monitor Session State Reason Description ------- ----------- ---------------------- -------------------------------- 1 up The session is up This workaround must be performed while no sFlow data sources are configured.

Further Problem Description