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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
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Chapter 26 Configuring SPAN and RSPAN
SPAN and RSPAN Session Limits
•
Inactive VLANs are not allowed for VSPAN configuration.
•
A VSPAN session is made inactive if any of the source VLANs become RSPAN VLANs.
Trunk VLAN Filtering
In software release 6.3(1) and later releases, you can enter the filter keyword to select a set of VLANs
in a trunk that is used in a SPAN session. Trunk VLAN filtering is the analysis of network traffic on a
selected set of VLANs on trunk source ports. If you specify a set of VLANs with the filter keyword, the
traffic that is spanned by the session is limited to the VLANs that are specified. You can combine trunk
VLAN filtering with other source ports that belong to any of the selected VLANs, and you can also use
trunk VLAN filtering for RSPAN. Based on the traffic type (ingress, egress, or both), SPAN sends a copy
of the network traffic in the selected VLANs to the destination port.
Use trunk VLAN filtering only with trunk source ports. If you combine trunk VLAN filtering with other
source ports that belong to VLANs that are not included in the selected list of filter VLANs, SPAN
includes only the ports that belong to one or more of the selected VLANs in the operational sources.
When a VLAN is cleared, it is removed from the VLAN filter list. A SPAN session is disabled if the
VLAN filter list becomes empty.
Trunk VLAN filtering is not applicable to VSPAN sessions.
Trunk VLAN filtering is available for local SPAN sessions and RSPAN sessions.
SPAN Traffic
All network traffic, including multicast and bridge protocol data unit (BPDU) packets, can be monitored
using SPAN (RSPAN does not support monitoring of BPDU packets).
SPAN and RSPAN Session Limits
You can configure (and store in NVRAM) up to five SPAN sessions in a Catalyst 4500 series switch. The
five sessions can be split any way between SPAN, RSPAN source, and RSPAN destination sessions.
Configuring SPAN
The following sections describe how to configure SPAN.
Understanding How SPAN Works
SPAN selects network traffic for analysis by a SwitchProbe device or other RMON probe. SPAN mirrors
traffic from one or more source ports (Ethernet, Fast Ethernet, or Gigabit Ethernet) on one or more
VLANs to a destination port for analysis (see
Figure 26-1
). In
Figure 26-1
, all traffic on Ethernet port 5
(the source port) is mirrored to Ethernet port 10. A network analyzer on Ethernet port 10 receives all
network traffic from Ethernet port 5 without being physically attached to it.