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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
Configuring SPAN
Figure 26-1 Example SPAN Configuration
For SPAN configuration, the source ports and the destination port must be on the same switch.
SPAN does not affect the switching of network traffic on source ports; copies of the packets that are
received or transmitted by the source ports are sent to the destination port.
SPAN Configuration Guidelines
This section describes the configuration guideslines for configuring SPAN:
•
Incoming traffic on the SPAN destination port is disabled by default. You can enable it by entering
the inpkts enable keywords. However, while the port receives traffic for its assigned VLAN, it does
not participate in spanning tree for that VLAN. To avoid creating spanning tree loops with incoming
traffic enabled, assign the SPAN destination port to an unused VLAN.
•
In software release 5.2 and later releases, with the inpkts keyword enabled, you can prevent the
switch from learning source MAC addresses from traffic that is received on the SPAN destination
port by entering the learning disable keywords. If you want the switch to learn source MAC
addresses from traffic that is received on the SPAN destination port, enter the learning enable
keywords. By default, the switch learns source MAC addresses from incoming traffic (learning
enable) if the inpkts keyword is enabled. The source MAC address learning options only affect
traffic that is received from a device that is attached to the SPAN destination port itself, not from
traffic that is mirrored from the SPAN source.
•
When monitoring a VLAN on a switch, you must monitor both transmit and receive traffic (both).
You cannot monitor only transmit (Tx) or only receive (Rx) traffic.
•
If you specify a set of VLANs with the filter keyword, the traffic that is spanned by the session is
limited to the VLANs specified.
•
You cannot configure SPAN on sc0.
•
Any traffic between two network nodes that are attached to a switch port that is configured as a
SPAN source port is not mirrored to the SPAN destination port. You can span local traffic that passes
through the switch.
•
You can have up to five SPAN sessions running at the same time with any combination of ingress
and egress sessions.
1 2 3 4 5 6 7 8 9 10 11 12
Port 5 traffic mirrored
on Port 10
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E8
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