Span And Rspan And Switch Stacks - Cisco Catalyst 3750-E Software Configuration Manual
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Also See for Catalyst 3750-E:
- Getting started manual (27 pages) ,
- Product support bulletin (6 pages) ,
- Configuration handbook (359 pages)
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Chapter 30
Configuring SPAN and RSPAN
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SPAN and RSPAN and Switch Stacks
Because the stack of switches is treated as one logical switch, local SPAN source ports and destination
ports can be in different switches in the stack. Therefore, the addition or deletion of switches in the stack
can affect a local SPAN session, as well as an RSPAN source or destination session. An active session
can become inactive when a switch is removed from the stack or an inactive session can become active
when a switch is added to the stack.
For more information about switch stacks, see
Understanding Flow-Based SPAN
You can control the type of network traffic to be monitored in SPAN or RSPAN sessions by using
flow-based SPAN (FSPAN) or flow-based RSPAN (FRSPAN), which apply access control lists (ACLs)
to the monitored traffic on the source ports. The FSPAN ACLs can be configured to filter IPv4, IPv6,
and non-IP monitored traffic.
You apply an ACL to a SPAN session through the interface. It is applied to all the traffic that is monitored
on all interfaces in the SPAN session.The packets that are permitted by this ACL are copied to the SPAN
destination port. No other packets are copied to the SPAN destination port.
The original traffic continues to be forwarded, and any port, VLAN, and router ACLs attached are
applied. The FSPAN ACL does not have any effect on the forwarding decisions. Similarly, the port,
VLAN, and router ACLs do not have any effect on the traffic monitoring. If a security input ACL denies
a packet and it is not forwarded, the packet is still copied to the SPAN destination ports if the FSPAN
ACL permits it. But if the security output ACL denies a packet and it is not sent, it is not copied to the
SPAN destination ports. However, if the security output ACL permits the packet to go out, it is only
copied to the SPAN destination ports if the FSPAN ACL permits it. This is also true for an RSPAN
session.
You can attach three types of FSPAN ACLs to the SPAN session:
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The security ACLs have higher priority than the FSPAN ACLs on a switch. If FSPAN ACLs are applied,
and you later add more security ACLs that cannot fit in the hardware memory, the FSPAN ACLs that you
applied are removed from memory to allow space for the security ACLs. A system message notifies you
of this action, which is called unloading. When there is again space for the FSPAN ACLs to reside in
memory, they are added to the hardware memory on the switch. A system message notifies you of this
action, which is called reloading. The IPv4, IPv6 and MAC FSPAN ACLs can be unloaded or reloaded
independently.
OL-9775-08
An IEEE 802.1x port can be a SPAN source port. You can enable IEEE 802.1x on a port that is a
SPAN destination port; however, IEEE 802.1x is disabled until the port is removed as a SPAN
destination.
For SPAN sessions, do not enable IEEE 802.1x on ports with monitored egress when ingress
forwarding is enabled on the destination port. For RSPAN source sessions, do not enable
IEEE 802.1x on any ports that are egress monitored.
IPv4 FSPAN ACL— filters only IPv4 packets.
IPv6 FSPAN ACL— filters only IPv6 packets.
MAC FSPAN ACL— filters only non-IP packets.
Chapter 5, "Managing Switch Stacks."
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
Understanding Flow-Based SPAN
30-11
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