Restrictions for Switched Port Analyzer
The restrictions for the Switched Port Analyzer (SPAN) are as follows:
-
SPAN filtering is not supported.
-
For SPAN sources, you can monitor traffic for a single port or a series or range of ports for each session.
-
The destination port cannot be a source port; a source port cannot be a destination port.
-
You cannot have two SPAN sessions using the same destination port.
-
You cannot have two SPAN sessions using the same source port.
-
When you configure a switch port as a SPAN destination port, it is no longer a normal switch port; only monitored traffic passes through the SPAN destination port.
-
Entering SPAN configuration commands does not remove previously configured SPAN parameters. You must enter the no monitor session session_number global configuration command to delete configured SPAN parameters.
-
You can configure a disabled port to be a source or destination port, but the SPAN function does not start until the destination port and at least one source port are enabled.
Traffic monitoring in a SPAN session has the following restrictions:
-
The device supports up to four local SPAN sessions.
-
SPAN sessions do not interfere with the normal operation of the device. However, an oversubscribed SPAN destination, for example, a 10-Mb/s port monitoring a 100-Mb/s port, can result in dropped or lost packets.
-
When SPAN is enabled, each packet being monitored is sent twice, once as normal traffic and once as a monitored packet. Monitoring a large number of ports could potentially generate large amounts of network traffic.
-
You can configure SPAN sessions on disabled ports; however, a SPAN session does not become active unless you enable the destination port and at least one source port for that session.