Configuring Local SPAN and ERSPAN

This chapter describes how to configure the Local and ER Ethernet switched port analyzer (SPAN) feature to monitor traffic.

Information About SPAN and ERSPAN

The Switched Port Analyzer (SPAN) feature (sometimes called port mirroring or port monitoring) allows network traffic to be analyzed by a network analyzer such as a Cisco SwitchProbe or other Remote Monitoring (RMON) probe.

SPAN lets you monitor traffic on one or more ports, or one or more VLANs, and send the monitored traffic to one or more destination ports where the network analyzer is attached.

SPAN Sources

The interfaces from which traffic can be monitored are called SPAN sources. These include Ethernet, virtual Ethernet, port-channel, and VLAN. When a VLAN is specified as a SPAN source, all supported interfaces in the VLAN are SPAN sources. Traffic can be monitored in the receive direction, the transmit direction, or both directions for Ethernet and virtual Ethernet source interfaces.

  • Receive source (Rx)—Traffic that enters the switch through this source port is copied to the SPAN destination port.
  • Transmit source (Tx)—Traffic that exits the switch through this source port is copied to the SPAN destination port.

Characteristics of Source Ports

A source port has these characteristics:

  • Can be port type Ethernet, virtual Ethernet, port-channel, or VLAN.
  • Cannot be a destination port.
  • Can be configured to monitor the direction of traffic —receive, transmit, or both.
  • Source ports can be in the same or different VLANs.
  • For VLAN SPAN sources, all active ports in the source VLAN are included as source ports.
  • Local SPAN sources must be on the same host (linecard) as the destination port.

SPAN Destinations

SPAN destinations refer to the interfaces that monitor source ports. This section includes the following topics:

Characteristics of Local SPAN Destination Ports

Each local SPAN session must have at least one destination port (also called a monitoring port) that receives a copy of traffic from the source ports or VLANs. A destination port has these characteristics:

  • Can be any physical or virtual Ethernet port or a port channel.
  • Cannot be a source port.
  • Is excluded from the source list and is not monitored if it belongs to a source VLAN of any SPAN session.
  • Receives copies of transmitted and received traffic for all monitored source ports. If a destination port is oversubscribed, it can become congested. This congestion can affect traffic forwarding on one or more of the source ports.
  • Must be on the same host (linecard) as the source port.
  • In Local SPAN, the source interface and destination interface are on the same device.
    See Figure 9-1, Local SPAN.

Characteristics of ERSPAN Destination Ports

  • An ERSPAN destination is specified by an IP address.
  • In ERSPAN, source SPAN interface and destination SPAN interface may be on different devices interconnected by an IP network. ERSPAN traffic is GRE-encapsulated. See Figure 9-2, ERSPAN.

Local SPAN

In Local SPAN, the source interface and destination interface are on the same device. The network analyzer is attached directly to the SPAN destination port. The SPAN source can be a port or a VLAN interface.The destination, although usually a port, could also be a VLAN.

Figure 9-1 shows that traffic transmitted by host A is received on the SPAN source interface. Traffic (ACLs, QoS, and so forth) is processed as usual. Traffic is then replicated. The original packet is forwarded on toward host B. The replicated packet is then sent to the destination SPAN interface where the monitor is attached.

Local SPAN can replicate to one or more destination ports. Traffic can be filtered so that only traffic of interest is sent out the destination SPAN interface.

Local SPAN can monitor all traffic received on the source interface including BPDUs.

Figure 9-1 Local SPAN

 

 

Encapsulated Remote SPAN

Encapsulated remote (ER) SPAN monitors traffic in multiple network devices across an IP network and sends that traffic in an encapsulated envelope to destination analyzers. In contrast, Local SPAN cannot forward traffic through the IP network. ERSPAN can be used to monitor traffic remotely. ERSPAN sources can be ports or VLANs.

In Figure 9-2, the ingress and egress traffic for host A are monitored using ERSPAN. Encapsulated ERSPAN packets are routed from host A through the routed network to the destination device where they are de-capsulated and forwarded to the attached network analyzer. The destination may also be on the same L2 network as the source.

Figure 9-2 ERSPAN

 

 

Network Analysis Module

You can also use the Cisco Network Analysis Module (NAM) to monitor ERSPAN data sources for application performance, traffic analysis, and packet header analysis.

To use NAM for monitoring the Cisco Nexus 1000V ERSPAN data sources see the Cisco Nexus 1010 Network Analysis Module Installation and Configuration Note, 4.2.

SPAN Sessions

You can create up to 64 total SPAN sessions (Local SPAN plus ERSPAN) on your local device.

You can configure an ERSPAN session ID that is added to the ERSPAN header of the encapsulated frame to differentiate between various ERSPAN streams of traffic at the termination box. You can also configure the range of flow ID numbers. For more information, see

You can also create a 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 9-3 shows a VLAN-based SPAN configuration that copies traffic from three VLANs to three specified destination ports. You can choose which VLANs to allow on each destination port to limit the traffic transmitted. In Figure 9-3, the device transmits packets from one VLAN at each destination port.

Note VLAN-based 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 transmit destination ports.

Figure 9-3 VLAN-based SPAN Configuration

.

SPAN Guidelines and Limitations

SPAN has the following configuration guidelines and limitations:

  • A maximum of 64 SPAN sessions (Local SPAN plus ERSPAN) can be configured on the VSM.
  • A maximum of 32 source VLANs are allowed in a session.
  • A maximum of 128 source interfaces are allowed in a session.
Caution Overload Potential
To avoid an overload on uplink ports, use caution when configuring ERSPAN, especially when sourcing VLANs.
  • A port can be configured in a maximum of 4 SPAN sessions.
  • The destination port used in one SPAN session cannot also be used as the destination port for another SPAN session.
  • You cannot configure a port as both a source and destination port.
  • In a SPAN session, packets that source ports receive may be replicated even though they are not transmitted on the ports. The following are examples of this behavior:

– Traffic that results from flooding

– Broadcast and multicast traffic

  • For VLAN SPAN sessions switched on the same VLAN with both receive and transmit configured, two packets (one from receive and one from transmit) are forwarded from the destination port.

Default Settings

Table 9-1 lists the SPAN default settings.

 

Table 9-1 SPAN Defaults

Parameters
Default

State

SPAN sessions are created in the shut state.

Description

blank

Traffic direction for the source interface

both

Configuring SPAN

This section describes how to configure SPAN and includes the following procedures.

Configuring a Local SPAN Session

Use this procedure to configure a SPAN session.

Note If you are configuring ERSPAN, see the Configuring an ERSPAN Session.

BEFORE YOU BEGIN

  • You are logged in to the CLI in EXEC mode.
  • You know the number of the SPAN session you are going to configure.
  • The source and destination ports are already configured in either access or trunk mode. For more information, see the Cisco Nexus 1000V Interface Configuration Guide, Release 4.0(4)SV1(3).
  • SPAN sessions are created in the shut state by default.
  • When you create a SPAN session that already exists, any additional configuration is added to that session. To make sure the session is cleared of any previous configuration, you can delete the session first (see Step 2, no monitor session).
  • This procedure involves creating the SPAN session in Monitor Configuration mode; and then, optionally, configuring allowed VLANs in Interface Configuration mode.

SUMMARY STEPS

1. config t

2. no monitor session session-number

3. monitor session session-number

4. description description

5. source {interface type | vlan} {number | range} [ rx | tx | both ]

6. (Optional) Repeat Step 5 to configure additional SPAN sources.

7. (Optional) filter vlan {number | range}

8. (Optional) Repeat Step 7 to configure all source VLANs to filter.

9. destination interface type {number | range}

10. (Optional) Repeat Step 9 to configure all SPAN destination ports.

11. no shut

12. (Optional) exit

13. (Optional) interface ethernet slot / port [- port ]

14. (Optional) switchport trunk allowed vlan { vlan-range | add vlan-range | except vlan-range | remove vlan-range | all | none }

15. (Optional) Repeat Step 13 and Step 14 to configure the allowed VLANs on each destination port.

16. (Optional) show interface ethernet slot / port [- port ] trunk

17. (Optional) copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

 

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2

no monitor session session-number

 

Example:

n1000v(config)# no monitor session 3

Clears the specified session.

Step 3

monitor session session-number

 

Example:

n1000v(config)# monitor session 3

n1000v(config-monitor)#

Creates a session with the given session number and places you in the CLI Monitor Configuration mode to further configure the session.

Step 4

description description

 

Example:

n1000v(config-monitor)# description my_span_session_3

For the specified SPAN session, adds a description.

  • description: up to 32 alphanumeric characters
    default = blank (no description)

Step 5

source {interface type | vlan}
{number | range} [ rx | tx | both ]

 

Example 1:

n1000v(config-monitor)# source interface ethernet 2/1-3, ethernet 3/1 rx

 

Example 2:

n1000v(config-monitor)# source interface port-channel 2

 

Example 3:

n1000v(config-monitor)# source interface vethernet 12 both

 

Example 4:

n1000v(config-monitor)# source vlan 3, 6-8 tx

For the specified session, configures the sources and the direction of traffic to monitor.

  • type: Specify the interface type—ethernet, port-channel, vethernet.
  • number: Specify the interface slot/port or range; or the VLAN number or range to monitor.
  • traffic direction: Specify traffic monitoring to be in one of the following directions:

– receive (rx) (the VLAN default)

– transmit (tx)

– both (the interface default)

Step 6

(Optional) Repeat Step 5 to configure additional SPAN sources.

Step 7

filter vlan {number | range}

 

Example:

n1000v(config-monitor)# filter vlan 3-5, 7

(Optional) For the specified SPAN session, configures the filter from among the source VLANs.

Step 8

(Optional) Repeat Step 7 to configure all source VLANs to filter.

Step 9

destination interface type
{number | range}

 

Example:

n1000v(config-monitor)# destination interface ethernet 2/5, ethernet 3/7

For the specified SPAN session, configures the port(s) to act as destination(s) for copied source packets.

  • type: Specify the interface type—ethernet or vethernet.
  • number: Specify the interface slot/port to monitor.
  • range: Specify the interface range to monitor.

Note SPAN destination ports must already be configured as either access or trunk ports.

Step 10

(Optional) Repeat Step 9 to configure all SPAN destination ports.

Step 11

no shut

 
Example:
n1000v(config-monitor)# no shut

Enables the SPAN session. By default, the session is created in the shut state.

Step 12

exit

 

Example:

n1000v(config-monitor)# exit

n1000v(config)#

(Optional) Exits Monitor Configuration mode and places you in CLI Configuration mode.

Step 13

interface ethernet slot / port [- port ]

 

Example:

n1000v(config)# interface ethernet 2/5

n1000v(config-if)#

(Optional) Places you in CLI Interface Configuration mode for the specified interface.

Step 14

switchport trunk allowed vlan { vlan-range | add vlan-range | except vlan-range | remove vlan-range | all | none }

 

Example:

n1000v(config-if)# switchport trunk allowed vlan 3-5

(Optional) For the specified interface. configures the range of VLANS that are allowed on the interface. By default all VLANs are allowed on the interface.

  • vlan-range: Specify a range of VLANs to be allowed on the interface.
  • add vlan-range: Add to the existing VLANs allowed on the interface.
  • except vlan-range: Exclude a range of VLANs from those allowed on the interface
  • remove vlan-range: Remove a range of VLANs from those allowed on the interface.
  • all: Allow all VLANs on the interface.
    This is the default.
  • none: Allow no VLANs on the interface.

Step 15

(Optional) Repeat Step 13 and Step 14 to configure the allowed VLANs on each destination port.

Step 16

show interface ethernet slot / port [- port ] trunk

 

Example:

n1000v(config-if)# show interface ethernet 2/5 trunk

(Optional) Displays the interface trunking configuration for the selected slot and port or range of ports.

Step 17

copy running-config startup-config

Example:

n1000v(config-if)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Configuring an ERSPAN Port Profile

Use this procedure to configure a port profile on the VSM to carry ERSPAN packets through the IP network to a remote destination analyzer.

BEFORE YOU BEGIN

  • You are logged in to the CLI in EXEC mode.
  • This configuration must be completed for all hosts in the vCenter Server.
  • You know the name to be used for this port profile.

Note The port profile name is used to configure the VMKNIC that is required on each of the ESX hosts.

  • You know the name of the VMware port group to which this profile maps.
  • You have the VMware documentation for adding a new virtual adapter.
  • You have already created the system VLAN and you know its VLAN ID which will be used in this configuration.

For more information about system port profiles, see the Cisco Nexus 1000V Port Profile Configuration Guide, Release 4.0(4)SV1(3).

  • The port profile used for ERSPAN must be configured for Layer 3 control. This procedure includes a step for making this configuration.
  • Only one VM kernel NIC can be assigned to this Layer 3 control port profile per host.

– If more than one VMware kernel NIC is assigned to a host, the last one assigned takes effect.

– If more than one VMware kernel NIC is assigned to a host, and you remove the second one assigned, then the VEM does not use the first one assigned. Instead, you must remove both VMware kernel NICs and then add one back.

  • The port profile must be an access port profile. It cannot be a trunk port profile. This procedure includes steps to configure the port profile as an access port profile.
  • For more information about creating a Layer 3 control port profile, see the Creating a Port Profile for Layer 3 Control.

SUMMARY STEPS

1. config t

2. port-profile port_profile_name

3. capability l3control

4. vmware port-group pg_name

5. switchport mode access

6. switchport access vlan vlan_id

7. no shutdown

8. system vlan vlan_id

9. state enabled

10. (Optional) show port-profile name port_profile_name

11. (Optional) copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

 

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2

port-profile port_profile_name

 

Example:

n1000v(config)# port-profile erspan_profile

n1000v(config-port-prof)#

Creates the port profile and places you into CLI Global Configuration mode for the specified port profile. Saves the port profile in the running configuration.

The port-profile name can be up to 80 characters and must be unique for each port profile on the Cisco Nexus 1000V.

Step 3

capability l3control

 

Example:

n1000v(config-port-prof)# capability l3control

n1000v(config-port-prof)#

Configures the port-profile to carry ERSPAN packet traffic through the IP network and saves this in the running configuration.

Step 4

vmware port-group pg_name

 

Example:

n1000v(config-port-prof)#vmware port-group erspan

n1000v(config-port-prof)#

Designates the port profile as a VMware port group and adds the name of the VMware port group to which this profile maps. Saves the settings in the running configuration.

The port profile is mapped to a VMware port group of the same name. When a vCenter Server connection is established, the port group created in Cisco Nexus 1000V is then distributed to the virtual switch on the vCenter Server.

  • pg-name: Port group name. If you do not specify a pg-name, then the port group name will be the same as the port profile name. If you want to map the port profile to a different port group name, use the pg-name option followed by the alternate name.

Step 5

switchport mode access

 

Example:

n1000v(config-port-prof)# switchport mode access

n1000v(config-port-prof)#

Designates the interfaces as switch access ports (the default).

Step 6

switchport access vlan vlan_id

 

Example 1:

n1000v(config-port-prof)# switchport access vlan 2

n1000v(config-port-prof)#

Assigns a VLAN ID to the access port for this port profile and saves the setting in the running configuration.

Step 7

no shutdown

 

Example:

n1000v(config-port-prof)# no shutdown

n1000v(config-port-prof)#

Enables the interface in the running configuration.

Step 8

system vlan vlan_id

 

Example:

n1000v(config-port-prof)# system vlan 2

n1000v(config-port-prof)#

Associates the system VLAN ID with the port profile and saves it in the running configuration.

Must match the VLAN ID assigned to the access port. If it does not match, then the following error message is generated:

ERROR: System vlan being set does not match the switchport access vlan 2

Step 9

state enabled

 

Example:

n1000v(config-port-prof)# state enabled

n1000v(config-port-prof)#

Enables the port profile in the running configuration.

This port profile is now ready to send out ERSPAN packets on all ESX Hosts with ERSPAN sources

Step 10

show port-profile name port_profile_name

 

Example:

n1000v(config-port-prof)# show port-profile name erspan

port-profile erspan

description:

status: enabled

capability uplink: no

capability l3control: yes

system vlans: 2

port-group: access

max-ports: 32

inherit:

config attributes:

switchport access vlan 2

no shutdown

evaluated config attributes:

switchport access vlan 2

no shutdown

assigned interfaces:

 

n1000v(config-port-prof)#

(Optional) Displays the configuration for the specified port profile as it exists in the running configuration.

Step 11

copy running-config startup-config

Example:

n1000v(config-port-prof)# copy running-config startup-config

[########################################] 100%

n1000v(config-port-prof)#

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Step 12

Using the VMware documentation, go to vSphere Client and configure a VMKNIC on each ESX Host. Make sure the VMKNIC points to this port profile as a new virtual adapter.

Configuring an ERSPAN Session

Use this procedure to configure an ERSPAN session.

Note If you are configuring Local SPAN, see the Configuring a Local SPAN Session.

BEFORE YOU BEGIN

  • You are logged in to the CLI in EXEC mode.
  • You know the number of the SPAN session you are going to configure.
  • You have already configured an ERSPAN-capable port profile on the VSM using the Configuring an ERSPAN Port Profile.
  • Using the VMware documentation for adding a new virtual adapter, you have already configured the required VMKNIC on each of the ESX hosts.
  • SPAN sessions are created in the shut state by default.
  • When you create a SPAN session that already exists, any additional configuration is added to that session. To make sure the session is cleared of any previous configuration, you can delete the session first (see Step 2, no monitor session).
  • This procedure involves creating the SPAN session in ERSPAN Source Configuration mode.

SUMMARY STEPS

1. config t

2. no monitor session session-number

3. monitor session session-number type erspan-source

4. description description

5. source {interface type | vlan} {number | range} [ rx | tx | both ]

6. (Optional) Repeat Step 5 to configure additional ERSPAN sources.

7. (Optional) filter vlan {number | range}

8. (Optional) Repeat Step 7 to configure all source VLANs to filter.

9. destination ip ip_address

10. (Optional) ip ttl ttl_value

11. (Optional) ip prec ipp_value

12. (Optional) ip dscp dscp_value

13. (Optional) mtu mtu_value

14. erspan-id flow_id

15. no shut

16. (Optional) show monitor session session_id

17. (Optional) exit

18. (Optional) copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

 

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2

no monitor session session-number

 

Example:

n1000v(config)# no monitor session 3

Clears the specified session.

Step 3

monitor session session-number type erspan-source

 

Example:

n1000v(config)# monitor session 3 type erspan

n1000v(config-erspan-source)#

Creates a session with the given session number and places you in the CLI ERSPAN Source Configuration mode. This configuration is saved in the running configuration.

Step 4

description description

Example:

n1000v(config-erspan-src)# description my_erspan_session_3

n1000v(config-erspan-src)#

For the specified ERSPAN session, adds a description and saves it in the running configuration.

  • description: up to 32 alphanumeric characters
    default = blank (no description)

Step 5

source { interface type | vlan }
{ number | range } [ rx | tx | both ]

 

Example 1:

n1000v(config-erspan-src)# source interface ethernet 2/1-3, ethernet 3/1 rx

 

Example 2:

n1000v(config-erspan-src)# source interface port-channel 2

 

Example 3:

n1000v(config-erspan-src)# source interface vethernet 12 both

 

Example 4:

n1000v(config-erspan-src)# source vlan 3, 6-8 tx

For the specified session, configures the source(s) and the direction of traffic to monitor, and saves them in the running configuration.

  • type: Specify the interface type—ethernet, port-channel, vethernet.
  • number: Specify the interface slot/port or range; or the VLAN number or range to monitor.
  • traffic direction: Specify traffic monitoring to be in one of the following directions:

– receive (rx) (the VLAN default)

– transmit (tx)

– both (the interface default)

Step 6

(Optional) Repeat Step 5 to configure additional ERSPAN sources.

Step 7

filter vlan { number | range }

 

Example:

n1000v(config-erspan-src)# filter vlan 3-5, 7

(Optional) For the specified ERSPAN session, configures the VLANs, VLAN lists, or VLAN ranges to be monitored; and saves this in the running configuration.

On the monitor port, only the traffic from the VLANs which match the VLAN filter list are replicated to the destination.

Step 8

(Optional) Repeat Step 7 to configure all source VLANs to filter.

Step 9

destination ip ip_address

 

Example:

n1000v(config-erspan-src)# destination ip 10.54.54.1

n1000v(config-monitor-erspan-src)#

Configures the IP address of the host to which the encapsulated traffic is sent and saves it in the running configuration.

Step 10

ip ttl ttl_value

 

Example:

n1000v(config-monitor-erspan-src)# ip ttl 64

n1000v(config-monitor-erspan-src)#

(Optional) Specifies the IP time-to-live value, from 1-255, for the packets in the ERSPAN traffic, and saves it in the running configuration.

Step 11

ip prec precedence_value

 

Example:

n1000v(config-monitor-erspan-src)# ip prec 1

n1000v(config-monitor-erspan-src)#

(Optional) Specifies the IP precedence value, from 0-7, for the packets in the ERSPAN traffic, and saves it in the running configuration.

Step 12

ip dscp dscp_value

 

Example:

n1000v(config-monitor-erspan-src)# ip dscp 24

n1000v(config-monitor-erspan-src)#

(Optional) Specifies the IP DSCP value, from 0-63. for the packets in the ERSPAN traffic, and saves it in the running configuration.

Step 13

mtu mtu_value

 

Example:

n1000v(config-monitor-erspan-src)# mtu 1000

n1000v(config-monitor-erspan-src)#

(Optional) Specifies an MTU size for the ERSPAN traffic, and saves it in the running configuration.

Step 14

erspan-id flow_id

 

Example:

n1000v(config-erspan-src)# erspan-id 51

Adds an ERSPAN ID (1-1023) to the session configuration and saves it in the running configuration.

The session ERSPAN ID is added to the ERSPAN header of the encapsulated frame and can be used at the termination box to differentiate between various ERSPAN streams of traffic.

Step 15

no shut

 
Example:
n1000v(config-erspan-src)# no shut

Enables the ERSPAN session and saves it in the running configuration.

By default, the session is created in the shut state.

Step 16

show monitor session session_id

 

Example:
n1000v(config-erspan-src)# show monitor session 3

(Optional) Displays the ERSPAN session configuration as it exists in the running configuration.

Step 17

exit

 

Example:

n1000v(config-erspan-src)# exit

n1000v(config)#

(Optional) Exits ERSPAN Source Configuration mode and returns you to CLI Configuration mode.

Step 18

copy running-config startup-config

Example:

n1000v(config)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Shutting Down a SPAN Session

Use this procedure to discontinue the copying of packets for a SPAN session. You can discontinue copying packets from one souce and destination; and then resume for another source and destination.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

  • You are logged in to the CLI in EXEC mode.
  • You know which SPAN session that you want to shut down.
  • You can shut down a SPAN session from either Global Configuration mode or Monitor Configuration mode.

SUMMARY STEPS

From Global Configuration mode:

1. config t

2. monitor session {session-number | session-range | all } shut

3. show monitor

4. copy running-config startup-config

From Monitor Configuration mode:

1. config t

2. monitor session {session-number | session-range | all } [type erspan-source]

3. shut

4. show monitor

5. copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

Example:

n1000v# config t

n1000v(config)#

Places you into CLI Global Configuration mode.

Step 2

monitor session { session-number | session-range | all } shut

Example:

n1000v(config)# monitor session 3 shut

n1000v(config)#

 

Example:

n1000v(config)# monitor session 3

n1000v(config-monitor)# shut

Shuts down the specified SPAN monitor session(s)) from either Global Configuration mode or Monitor-Configuration mode.

  • session-number: Specifies a particular SPAN session number.
  • session range: Specifies a range of SPAN sessions (allowable = from 1 to 16).
  • all: Specifies all SPAN monitor sessions.

Step 3

show monitor

Example:

n1000v(config-monitor)# show monitor

(Optional) Displays the status of the SPAN sessions.

Step 4

copy running-config startup-config

Example:

n1000v(config-monitor)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

 

Resuming a SPAN Session

Use this procedure to resume the copying of packets for a SPAN session. You can discontinue copying packets from one souce and destination; and then resume for another source and destination.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

  • You are logged in to the CLI in EXEC mode.
  • You know which SPAN session that you want to configure.
  • You can resume the SPAN session from either Global Configuration mode or Monitor Configuration mode.

SUMMARY STEPS

From Global Configuration mode:

1. config t

2. no monitor session {session-number | session-range | all } shut

3. show monitor

4. copy running-config startup-config

From Monitor Configuration mode:

1. config t

2. monitor session {session-number | session-range | all } [type erspan-source]

3. no shut

4. show monitor

5. copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

Example:

n1000v# config t

n1000v(config)#

Places you into CLI Global Configuration mode.

Step 2

[ no ] monitor session { session-number session-range | all } shut

Example:

n1000v(config)# no monitor session 3 shut

n1000v(config)#

 

Example:

n1000v(config)# monitor session 3

n1000v(config-monitor)# no shut

Starts the specified SPAN monitor session(s) from either Global Configuration mode or Monitor-Configuration mode.

  • session-number: Specifies a particular SPAN session number.
  • session range: Specifies a range of SPAN sessions (allowable = from 1 to 16).
  • all: Specifies all SPAN monitor sessions.

Step 3

show monitor

Example:

n1000v(config-monitor)# show monitor

(Optional) Displays the status of the SPAN sessions.

Step 4

copy running-config startup-config

Example:

n1000v(config-monitor)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Configuring the Allowable ERSPAN Flow IDs

Use this procedure to restrict the allowable range of flow IDs that can be assigned to ERSPAN sessions.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

  • You are logged in to the CLI in EXEC mode.
  • You know the restricted range of ERSPAN flow IDs that you want to designate.
  • The available ERSPAN flow IDs are 1-1024. You can restrict the range of available IDs using this procedure.

SUMMARY STEPS

1. config t

2. [no] limit-resource erspan-flow-id minimum min_val maximum max_val

3. copy running-config startup-config

DETAILED STEPS

 

Command
Purpose

Step 1

config t

Example:

n1000v# config t

n1000v(config)#

Places you into CLI Global Configuration mode.

Step 2

limit-resource erspan-flow-id minimum min_val maximum max_val

Example:

n1000v(config)# limit-resource erspan-flow-id minimum 20 maximum 40

n1000v(config)#

 

Restricts the allowable range of ERSPAN flow IDs that can be assigned.

Step 3

copy running-config startup-config

Example:

n1000v(config-monitor)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Verifying the SPAN Configuration

To verify the SPAN configuration, use the following commands:

 

Command
Purpose

show monitor session { all | session-number | range session-range } [ brief ]

Displays the SPAN session configuration.

show monitor

Displays Ethernet SPAN information.

module vem module-number execute vemcmd show span

Displays the configured SPAN sessions on a VEM module.

show port-profile name port_profile_name

Displays the Layer 3 capable port profile that is required for ERSPAN.

Example Configurations

This section includes the following example configurations:

Example Configuration for a SPAN Session

To configure a SPAN session, follow these steps:

Step 1 Configure destination ports in access or trunk mode, and enable SPAN monitoring.

n1000v# config t
n1000v(config)# interface ethernet 2/5
n1000v(config-if)# switchport
n1000v(config-if)# switchport mode trunk
n1000v(config-if)# no shut
n1000v(config-if)# exit
n1000v(config)#
 

Step 2 Configure a SPAN session.

n1000v(config)# no monitor session 3
n1000v(config)# monitor session 3
n1000v(config-monitor)# source interface ethernet 2/1-3
n1000v(config-monitor)# source interface port-channel 2
n1000v(config-monitor)# source vlan 3, 6-8 tx
n1000v(config-monitor)# filter vlan 3-5, 7
n1000v(config-monitor)# destination interface ethernet 2/5
n1000v(config-monitor)# no shut
n1000v(config-monitor)# exit
n1000v(config)# show monitor session 3
n1000v(config)# copy running-config startup-config
 

 

Example Configuration for an ERSPAN Session

The following example shows how to create a bidirectional ERSPAN session for a source Ethernet interface and destination IP address. Packets arriving at the destination IP are identified by the ID 999 in their header.

n1000v(config)# monitor session 1 type erspan-source
n1000v(config-erspan-src)# source interface ethernet 3/3
n1000v(config-erspan-src)# destination ip 10.54.54.1
n1000v(config-erspan-src)# erspan-id 999
n1000v(config-erspan-src)# mtu 1000
n1000v(config-erspan-src)# no shut
 
n1000v(config)# show monitor session 1
session 1
---------------
type : erspan-source
state : up
source intf :
rx : Eth3/3
tx : Eth3/3
both : Eth3/3
source VLANs :
rx :
tx :
both :
filter VLANs : filter not specified
destination IP : 10.54.54.1
ERSPAN ID : 999
ERSPAN TTL : 64
ERSPAN IP Prec. : 0
ERSPAN DSCP : 0
ERSPAN MTU : 1000
 
n1000v# module vem 3 execute vemcmd show span
 
VEM SOURCE IP: 10.54.54.10
 
HW SSN ID DST LTL/IP ERSPAN ID
0 10.54.54.1 999
1 48 local
 

Additional References

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

Related Documents

 

Related Topic
Document Title

Port profile configuration

Cisco Nexus 1000V Port Profile Configuration Guide, Release 4.0(4)SV1(3)

Interface configuration

Cisco Nexus 1000V Interface Configuration Guide, Release 4.0(4)SV1(3)

Complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco Nexus 1000V Command Reference, Release 4.0(4)SV1(3)

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.

—

Feature History for SPAN and ERSPAN

This section provides the SPAN and ERSPAN feature release history.

 

Feature Name
Releases
Feature Information

NAM support for ERSPAN data sources

4.0(4)SV1(3)

NAM support was introduced.

ERSPAN Type III header

4.0(4)SV1(3)

ERSPAN Type III header format was introduced.

SPAN and ERSPAN

4.0(4)SV1(1)

SPAN and ERSPAN were introduced.