SPAN
This chapter describes how to identify and resolve problems that relate to SPAN and includes the following topics:
Information About SPAN
The Switched Port Analyzer (SPAN) feature (sometimes called port mirroring or port monitoring) selects network traffic for analysis by a network analyzer. The network analyzer can be a Cisco SwitchProbe or other Remote Monitoring (RMON) probe.
The Cisco Nexus 1000VE supports two types of SPAN:
- SPAN (local SPAN) that can monitor sources within a host or VSE.
- Encapsulated remote SPAN (ERSPAN) that can send monitored traffic to an IP destination.
For detailed information about how to configure local SPAN or ERSPAN, see the Cisco Nexus 1000VE System Management Configuration Guide.
SPAN Session Guidelines
The following are SPAN session guidelines:
- When a SPAN session contains multiple transmit source ports, packets that these ports receive might be replicated even though they are not transmitted on the ports. Examples include the following:
– Traffic that results from flooding
– Broadcast and multicast traffic
- For VLAN SPAN sessions with both receive and transmit configured, two packets (one from receive and one from transmit) are forwarded from the destination port if the packets get switched on the same VLAN.
- After VMotion, the following might occur:
– A session is stopped if the source and destination ports are separated.
– A session resumes if the source and destination ports end up on the same host.
– The limit of 64 SPAN sessions is not exceeded.
– At least one operational source is configured.
– At least one operational destination is configured.
– The configured source and destination are on the same host.
– The session is enabled with the no shut command.
– All the source ports go down or are removed.
– All the destination ports go down or are removed.
– All the source and destination ports are separated by VMotion.
Problems with SPAN
The following are symptoms, possible causes, and solutions for problems with SPAN.
SPAN Troubleshooting Commands
You can use the commands in this section to troubleshoot problems related to SPAN.
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Displays the current state of a SPAN session, the reason it is down, and the session configuration. |
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- show monitor internal errors
- show monitor internal event-history msgs
- show monitor internal info global-info
- show monitor internal mem-stats
Example 14-1 show monitor Command
Example 14-2 show monitor session Command
Example 14-3 module vse execute vemcmd show span Command