Monitoring Network Traffic Using SPAN
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Each SPAN session represents an association of one destination with a set of source(s) along with
various other parameters that you specify to monitor the network traffic. One destination can be used by
one or more SPAN sessions. You can configure up to 16 SPAN sessions in a switch. Each session can
have several source ports and one destination port.
To activate any SPAN session, at least one source and the SD port must be up and functioning. Otherwise,
traffic is not directed to the SD port.
A source can be shared by two sessions, however, each session must be in a different direction—one
ingress and one egress.
You can temporarily deactivate (suspend) any SPAN session. The traffic monitoring is stopped during
You can perform VSAN-based filtering to selectively monitor network traffic on specified VSANs. You
can apply this VSAN filter to all sources in a session (see
You can specify session VSAN filters that are applied to all sources in the specified session. These filters
are bidirectional and apply to all sources configured in the session.
Guidelines to Specifying Filters
The following guidelines apply to SPAN filters:
SD Port Characteristics
An SD port has the following characteristics:
OL-16184-01, Cisco MDS SAN-OS Release 3.x
PortChannel configurations are applied to all ports in the PortChannel.
If no filters are specified, the traffic from all active VSANs for that interface is spanned by default.
While you can specify arbitrary VSAN filters in a session, traffic can only be monitored on the port
VSAN or on allowed-active VSANs in that interface.
Allows data traffic only in the egress (Tx) direction.
Does not require a device or an analyzer to be physically connected.
Supports only 1 Gbps or 2 Gbps speeds. The auto speed option is not allowed.
Multiple sessions can share the same destination ports.
If the SD port is shut down, all shared sessions stop generating SPAN traffic.
The outgoing frames can be encapsulated in Extended Inter-Switch Link (EISL) format.
52-4). Only VSANs present in the filter
Cisco MDS 9000 Family CLI Configuration Guide