Span Traffic - Cisco Catalyst 4500 Series Configuration Manual

About SPAN and RSPAN
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SPAN Traffic

You can use local SPAN to monitor all network traffic, including multicast and bridge protocol data unit
(BPDU) packets, Cisco Discovery Protocol (CDP), VLAN Trunk Protocol (VTP), Dynamic Trunking
Protocol (DTP), Spanning Tree Protocol (STP), and Port Aggregation Protocol (PAgP) packets. You
cannot use RSPAN to monitor Layer 2 protocols. See the
page 55-16
In some SPAN configurations, multiple copies of the same source packet are sent to the SPAN
destination port. For example, a bidirectional (both Rx and Tx) SPAN session is configured for the
sources a1 Rx monitor and the a2 Rx and Tx monitor to destination port d1. If a packet enters the switch
through a1 and is switched to a2, both incoming and outgoing packets are sent to destination port d1.
Both packets are the same (unless a Layer-3 rewrite occurs, in which case the packets are different
because of the added Layer 3 information).
SPAN and RSPAN Session Limits
You can configure a maximum of sixteen SPAN/RSPAN sessions (eight concurrent sessions with
ingress-only sources and eight concurrent sessions with egress-only sources). Bidirectional sources
count as both ingress and egress. RSPAN destination sessions count as a session containing an ingress
source.
Default SPAN and RSPAN Configuration
Table 55-1
Table 55-1
Feature
SPAN state
Source port traffic to monitor
Filters
Encapsulation type (destination port)
Ingress forwarding (destination port)
Host learning (destination port)
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
55-6
VSPAN monitors only traffic that enters the switch, not traffic that is routed between VLANs. For
example, if a VLAN is being Rx-monitored, and the multilayer switch routes traffic from another
VLAN to the monitored VLAN, that traffic is not monitored and is not received on the SPAN
destination port.
You cannot use filter VLANs in the same session with VLAN sources.
You can monitor only Ethernet VLANs.
for more information.)
shows the default SPAN and RSPAN configuration.
Default SPAN and RSPAN Configuration
Chapter 55
"RSPAN Configuration Guidelines" section on
Default Setting
Disabled.
Both received and sent traffic (both).
All VLANs, all packet types, all address types.
Native form (no encapsulation type header).
Disabled.
Disabled.
Configuring SPAN and RSPAN
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