Cisco DCNM Fundamentals Configuration Guide, Release 4.1
Configuring SPAN
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Configuring SPAN

Table Of Contents

Configuring SPAN

Information About SPAN

SPAN Sources

Characteristics of Source Ports

SPAN Destinations

Characteristics of Destination Ports

SPAN Sessions

Virtual SPAN Sessions

Multiple SPAN Sessions

High Availability

Virtualization Support

Licensing Requirements for SPAN

Prerequisites for SPAN

Guidelines and Limitations

Configuring SPAN

Configuring a SPAN Session

Configuring a Virtual SPAN Session

Configuring an RSPAN VLAN

Shutting Down or Resuming a SPAN Session

Field Descriptions for SPAN

Local SPAN Session: Configuration: Session Settings Section

Local SPAN Session: Configuration: Source and Destination Section

Additional References

Related Documents

Standards


Configuring SPAN


This chapter describes how to configure an Ethernet switched port analyzer (SPAN) in Cisco Data Center Network Manager (DCNM).

This chapter includes the following sections:

Information About SPAN

Licensing Requirements for SPAN

Prerequisites for SPAN

Guidelines and Limitations

Configuring SPAN

Field Descriptions for SPAN

Additional References

Information About SPAN

SPAN analyzes all traffic between source ports by directing the SPAN session traffic to a destination port with an external analyzer attached to it.

You can define the sources and destinations to monitor in a SPAN sessions on the local device.

This section includes the following topics:

SPAN Sources

SPAN Destinations

SPAN Sessions

Virtual SPAN Sessions

Multiple SPAN Sessions

High Availability

Virtualization Support

SPAN Sources

The interfaces from which traffic can be monitored are called SPAN sources. Sources designate the traffic to monitor and whether to copy ingress, egress, or both directions of traffic. SPAN sources include the following:

Ethernet ports

VLANs—When a VLAN is specified as a SPAN source, all supported interfaces in the VLAN are SPAN sources.

Remote SPAN (RSPAN) VLANs


Note A single SPAN session can include mixed sources in any combination of the above.


Characteristics of Source Ports

SPAN source ports have the following characteristics:

A port configured as a source port cannot also be configured as a destination port.

An RSPAN VLAN can only be used as a SPAN source.

SPAN Destinations

SPAN destinations refer to the interfaces that monitor source ports. Destination ports receive the copied traffic from SPAN sources.

Characteristics of Destination Ports

SPAN destination ports have the following characteristics:

Destinations for a SPAN session include Ethernet ports or port-channel interfaces in either access or trunk mode.

A port configured as a destination port cannot also be configured as a source port.

A destination port can be configured in only one SPAN session at a time.

Destination ports do not participate in any spanning tree instance. SPAN output includes Bridge Protocol Data Unit (BPDU) Spanning Tree Protocol hello packets.

An RSPAN VLAN can not be used as a SPAN destination.

You can configure SPAN destinations to inject packets to disrupt a certain TCP packet stream in support of the Intrusion Detection System (IDS).

You can configure SPAN destinations to enable a forwarding engine to learn the MAC address of the IDS.

SPAN Sessions

You can create up to 18 SPAN sessions designating sources and destinations to monitor.


Note Only two SPAN sessions can be running simultaneously.


Figure 12-1 shows a SPAN configuration. Packets on three Ethernet ports are copied to destination port Ethernet 2/5. Only traffic in the direction specified is copied.

Figure 12-1 SPAN Configuration

.

Virtual SPAN Sessions

You can create a virtual SPAN session to monitor multiple VLAN sources and choose only VLANs of interest to transmit on multiple destination ports. For example, you can configure SPAN on a trunk port and monitor traffic from different VLANs on different destination ports.

Figure 12-2 shows a virtual SPAN configuration. The virtual SPAN session copies traffic from the three VLANs to the three specified destination ports. You can choose which VLANs to allow on each destination port to limit the traffic that the device transmits on it. In Figure 12-2, the device transmits packets from one VLAN at each destination port.


Note Virtual SPAN sessions cause all source packets to be copied to all destinations, whether the packets are required at the destination or not. VLAN traffic filtering occurs at the egress destination port level.


Figure 12-2 Virtual SPAN Configuration

.

For information about configuring a virtual SPAN session, see the "Configuring a Virtual SPAN Session" section.

Multiple SPAN Sessions

Although you can define up to 18 SPAN sessions, only two SPAN sessions can be running simultaneously. You can shut down an unused SPAN session.

For information about shutting down SPAN sessions, see the "Shutting Down or Resuming a SPAN Session" section.

High Availability

The SPAN feature supports stateless and stateful restarts. After a reboot or supervisor switchover, Cisco NX-OS applies the running configuration.

Virtualization Support

A virtual device context (VDC) is a logical representation of a set of system resources. SPAN applies only to the VDC where the commands are entered.

For information about configuring VDCs, see the Cisco DCNM Virtual Device Context Configuration Guide, Release 4.1 at the following URL:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/dcnm/virtual_device_context/configuration/guide/vdc_dcnm_book.html

Licensing Requirements for SPAN

The following table shows the licensing requirements for this feature:

Product
License Requirement

DCNM

SPAN requires no license. Any feature not included in a license package is bundled with the Cisco Data Center Network Manager (DCNM) and is provided at no charge to you. For a complete explanation of the DCNM licensing scheme, see the Cisco DCNM Fundamentals Configuration Guide, Release 4.1.

NX-OS

SPAN requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide, Release 4.1 at the following URL:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/nx-os/licensing/configuration/guide/nx-os_licensing.html


Prerequisites for SPAN

SPAN has the following prerequisites:

You must first configure the ports on each device to support the desired SPAN configuration. For more information, see the Cisco DCNM Interfaces Configuration Guide, Release 4.1 at the following URL:
http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/dcnm/interfaces/configuration/guide/if_dcnm_book.html

Guidelines and Limitations

SPAN has the following configuration guidelines and limitations:

A maximum of 18 SPAN sessions can be configured on a device.

A maximum of two SPAN sessions can be running simultaneously on a device.

A destination port can only be configured in one SPAN session at a time.

You cannot configure a port as both a source and destination port.

A single SPAN session can include mixed sources in any combination of the following:

Ethernet ports

VLANs

Destination ports do not participate in any spanning tree instance. SPAN output includes Bridge Protocol Data Unit (BPDU) Spanning Tree Protocol hello packets.

When a SPAN session contains multiple egress source ports, packets that these ports receive may be replicated even though they are not transmitted on the ports. Some examples of this behavior on source ports are as follows:

Traffic that results from flooding

Broadcast and multicast traffic

For VLAN SPAN sessions with both ingress and egress configured, two packets (one from ingress and one from egress) are forwarded from the destination port if the packets get switched on the same VLAN.

VLAN SPAN monitors only the traffic that leaves or enters Layer 2 ports in the VLAN.

You can configure an RSPAN VLAN for use only as a SPAN session source.

You can configure a SPAN session on the local device only.

If you configure a SPAN session to monitor a routed interface, only the received traffic is captured, even if the session is configured for both directions. This limitation is only for traffic that enters a Layer 2 interface (with SVI as a Layer 3 interface) and then exits a routed (physical Layer 3) interface, which is the source of the monitor session. If traffic enters a routed (physical Layer 3) interface and exits another routed (physical Layer 3) interface, which is the source of the monitor session, then the destination port of the monitor session captures traffic in both directions. A SPAN session captures traffic in both directions if traffic entering the routed port is destined to an IP address (SVI) on the switch.

Configuring SPAN

This section includes the following topics:

Configuring a SPAN Session

Configuring a Virtual SPAN Session

Configuring an RSPAN VLAN

Shutting Down or Resuming a SPAN Session

Configuring a SPAN Session

You can configure a SPAN session on the local device only. By default, SPAN sessions are created in the shut state.

For sources, you can specify Ethernet ports, port channels, VLANs, and RSPAN VLANs. You can specify private VLANs (primary, isolated, and community) in SPAN sources.

For destination ports, you can specify Ethernet ports or port channels in either access or trunk mode. You must enable monitor mode on all destination ports.

BEFORE YOU BEGIN

A single SPAN session can include mixed sources in any combination of Ethernet ports or VLANs.

You must have already configured the destination ports in access or trunk mode. For more information, see the Cisco DCNM Interfaces Configuration Guide, Release 4.1 at the following URL:
http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/dcnm/interfaces/configuration/guide/if_dcnm_book.html

DETAILED STEPS

To configure a SPAN session, follow these steps:


Step 1 From the Feature Selector pane, choose Interfaces > Traffic Monitoring > SPAN. The available devices appear in the Summary pane.

Step 2 From the Summary pane, double-click the device that you want to configure with a SPAN session to display the configured SPAN sessions.

Step 3 (Optional) To delete a SPAN session that you are no longer using, right-click the SPAN session and choose Delete.

Step 4 (Optional) To configure a new SPAN session, from the menu bar choose File > New Local SPAN Session. By default, SPAN sessions are created in the shut state.

a. (Only the first time you create a SPAN session) From the Summary pane, double-click the device that you want to configure with a SPAN session to display the configured SPAN sessions.

b. (Optional) To modify the session number, from the Summary pane, double-click the Session Id field and enter a session number from 1 to 18.


Note You can only modify the session number immediately after you create the session.


Step 5 From the Summary pane, choose the SPAN session to configure.

Step 6 From the Details pane, click the Configuration tab and expand the Session Settings section, if necessary.

Step 7 (Optional) To add a description of the SPAN session, specify it in the Description field.

Step 8 (Optional) In the Filtered VLANs field, click the down arrow to display and choose from the configured VLANs.

Step 9 Add source Ethernet ports to the SPAN session as follows:

a. From the Ports association panel, double-click the device and then double-click the desired slot to display ports.

b. Choose the port, right-click on the port row, and choose Add to SPAN Source to add this port to the SPAN session sources.

Step 10 Add source VLANs or RSPAN VLANs to the SPAN session as follows:

a. From the VLANs association panel, double-click the device to display the configured VLANs.

b. Choose the VLAN, right-click on the VLAN row, and choose Add to SPAN Source to add this VLAN to the SPAN session sources.

Step 11 Add destination Ethernet ports to the SPAN session as follows:

a. From the Ports association panel, double-click the device and then double-click the desired slot to display ports.

b. Choose an access or trunk port.

c. In the Monitor column, check the check box to enable monitoring on this port.

d. Right-click on the port row and choose Add to SPAN Destination to add this port to the SPAN session destinations.

Step 12 (Optional) To modify SPAN session source settings, follow these steps:

a. From the Details pane, click the Configuration tab and expand the Source and Destination section, if necessary.

b. To modify the ingress or egress choice for a source, check or uncheck the Ingress or Egress check box to activate the desired direction to monitor. By default, both ingress and egress are monitored.

c. To delete a SPAN source or destination, choose the source or destination entry, right-click on it, and choose Delete.

Step 13 From the menu bar, choose File > Deploy to apply your changes to the device.


Configuring a Virtual SPAN Session

You can configure a virtual SPAN session to copy packets from source ports, VLANs, and RSPAN VLANs to destination ports on the local device. By default, SPAN sessions are created in the shut state.

For sources, you can specify ports, VLANs, or RSPAN VLANs.

For destination ports, you can specify Ethernet ports. You can choose which VLANs to allow on each destination port to limit the traffic that the device transmits on it.

BEFORE YOU BEGIN

You have already configured the destination ports in trunk mode. For more information, see the Cisco DCNM Interfaces Configuration Guide, Release 4.1 at the following URL:
http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/dcnm/interfaces/configuration/guide/if_dcnm_book.html

DETAILED STEPS

To configure a virtual SPAN session, follow these steps:


Step 1 From the Feature Selector pane, choose Interfaces > Traffic Monitoring > SPAN. The available devices appear in the Summary pane.

Step 2 From the Summary pane, double-click the device that you want to configure with a SPAN session to display the configured SPAN sessions.

Step 3 (Optional) To delete a SPAN session that you are no longer using, right-click the SPAN session and choose Delete.

Step 4 (Optional) To configure a new SPAN session, from the menu bar choose File > New Local SPAN Session. By default, SPAN sessions are created in the shut state.

a. (Only the first time you create a SPAN session) From the Summary pane, double-click the device that you want to configure with a SPAN session to display the configured SPAN sessions.

b. (Optional) To modify the session number, from the Summary pane, double-click the Session Id field and enter a session number from 1 to 18.


Note You can only modify the session number immediately after you create the session.


Step 5 From the Summary pane, choose the SPAN session to configure.

Step 6 From the Details pane, click the Configuration tab and expand the Session Settings section, if necessary.

Step 7 (Optional) To add a description of the SPAN session, specify it in the Description field.

Step 8 (Optional) To add VLANs to filter (include) in the SPAN session, in the Filtered VLANs field, click the down arrow to display and choose from the configured VLANs.

Step 9 Add source Ethernet ports to the SPAN session as follows:

a. From the Ports association panel, double-click the device and then double-click the desired slot to display ports.

b. Choose the port, right-click on the port row, and choose Add to SPAN Source to add this port to the SPAN session sources.

Step 10 Add source VLANs or RSPAN VLANs to the SPAN session as follows:

a. From the VLANs association panel, double-click the device to display the configured VLANs.

b. Choose the VLAN, right-click on the VLAN row, and choose Add to SPAN Source to add this VLAN to the SPAN session sources.

Step 11 Add destination Ethernet ports to the SPAN session as follows:

a. From the Ports association panel, double-click the device and then double-click the desired slot to display ports.

b. Choose an access or trunk port.

c. In the Monitor column, check the check box to enable monitoring on this port.

d. Right-click on the port row and choose Add to SPAN Destination to add this port to the SPAN session destinations.

Step 12 Limit the VLANs allowed on a trunk port by following these steps:

a. From the Feature Selector pane, choose Interfaces > Physical > Ethernet. The available devices appear in the Summary pane.

b. From the Summary pane, double-click the device and then double-click the slot that you want to configure.

c. Choose the trunk port to configure.

d. From the Details pane, click the Port Details tab and expand the Port Mode Settings section, if necessary.

e. Limit the VLANs on the trunk by clicking the Allowed VLANs field. The field displays configured VLANs that you can choose.

Step 13 From the menu bar, choose File > Deploy to apply your changes to the device.


Configuring an RSPAN VLAN

You can specify a remote SPAN (RSPAN) VLAN as a SPAN session source.

DETAILED STEPS

To configure an RSPAN VLAN, follow these steps:


Step 1 From the Feature Selector pane, choose Switching > VLAN. The available devices appear in the Summary pane.

Step 2 From the Summary pane, double-click the device that you want to configure.

Step 3 Choose the VLAN to configure.

Step 4 From the Details pane, click the VLAN Details tab and expand the Advanced Settings section, if necessary.

Step 5 Check the RSPAN VLAN check box.

Step 6 From the menu bar, choose File > Deploy to apply your changes to the device.


Shutting Down or Resuming a SPAN Session

You can shut down SPAN sessions to discontinue the copying of packets from sources to destinations. Because only two SPAN sessions can be running simultaneously, you can shut down one session in order to free hardware resources to enable another session. By default, SPAN sessions are created in the shut state.

You can resume (enable) SPAN sessions to resume the copying of packets from sources to destinations. In order to enable a SPAN session that is already enabled but operationally down, you must first shut it down and then enable it.

DETAILED STEPS

To shut down or resume (enable) a SPAN session, follow these steps:


Step 1 From the Feature Selector pane, choose Interfaces > Traffic Monitoring > SPAN.

The available devices appear in the Summary pane.

Step 2 From the Summary pane, double-click the device to display the configured SPAN sessions.

Step 3 From the Summary pane, choose the SPAN session to configure.

Step 4 From the Details pane, click the Configuration tab and expand the Session Settings section, if necessary.

Step 5 Resume (enable) the SPAN session by choosing Up in the Admin Status field.

Step 6 Shut down the SPAN session by choosing Down in the Admin Status field.


Note If a monitor session is enabled but its operational status is down, then to enable the session you must first shut down the session followed by resuming the session.



Field Descriptions for SPAN

This section includes the following field descriptions for SPAN:

Local SPAN Session: Configuration: Session Settings Section

Local SPAN Session: Configuration: Source and Destination Section

Local SPAN Session: Configuration: Session Settings Section

Table 12-1 Local SPAN Session: Configuration: Session Settings Section 

Element
Description

Session Id

Local SPAN session number that can only be specified when the session is first created. The value ranges from 1 to 18.

Description

Description for this session.

Filtered VLANs

When clicked, list of configured VLANs.

Admin Status

Administrative status of the session.

Operational Status

Display only. Whether the session is shut (down) or enabled (up).

Status Description

Display only. Status description.


Local SPAN Session: Configuration: Source and Destination Section

Table 12-2 Local SPAN Session: Configuration: Source and Destination Section 

Element
Description
Source

Interface/VLAN

Display only. Port or VLAN number.

Description

Display only. Port or VLAN description.

Ingress

Status of whether to monitor ingress packets.

Egress

Status of whether to monitor egress packets.

Destination

Interface

Display only. Port number.

Description

Display only. Port description.


Additional References

For additional information related to implementing SPAN, see the following sections:

Related Documents

Standards

Related Documents

Related Topic
Document Title

VDCs

Cisco DCNM Virtual Device Context Configuration Guide, Release 4.1 at the following URL:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/dcnm/virtual_device_context/configuration/guide/vdc_dcnm_book.html


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.