Cisco Nexus 5000 Series NX-OS Software Configuration Guide

Characteristics of Source Ports

A source port, also called a monitored port, is a switched interface that you monitor for network traffic analysis. The switch supports any number of ingress source ports (up to the maximum number of available ports on the switch) and any number of source VLANs or VSANs.

A source port has these characteristics:

• Can be of any port type: Ethernet, Fibre Channel, virtual Fibre Channel, port channel, SAN port channel, VLAN, and VSAN.
• Cannot be monitored in multiple SPAN sessions.
• Cannot be a destination port.
• Each source port can be configured with a direction (ingress, egress, or both) to monitor. For VLAN, VSAN, port channel, and SAN port channel sources, the monitored direction can only be ingress and applies to all physical ports in the group. The rx/tx option is not available for VLAN or VSAN SPAN sessions.
• Source ports can be in the same or different VLANs or VSANs.
• For VLAN or VSAN SPAN sources, all active ports in the source VLAN or VSAN are included as source ports.
• The switch supports a maximum of two egress SPAN source ports.

Note Consider a scenario in which an ERSPAN session and a local SPAN session is configured on a switch. Egress ports on both sessions are different. However, the ingress port on the local SPAN session is also receiving GRE-encapsulated traffic from the ERSPAN session. In such a scenario, the local SPAN session captures only the non-GRE-encapsulated traffic from the port that is defined as the source.

Characteristics of Destination Ports

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

• Can be any physical port, Ethernet, Ethernet (FCoE), or Fibre Channel, and virtual Fibre Channel ports cannot be destination ports.
• Cannot be a source port.
• Cannot be a port channel or SAN port channel group.
• Does not participate in spanning tree while the SPAN session is active.
• Is excluded from the source list and is not monitored if it belongs to a source VLAN of any SPAN session.
• Receives copies of sent 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.

Creating and Deleting a SPAN Session

You create a SPAN session by assigning a session number using the monitor command. If the session already exists, any additional configuration is added to that session.

To create a SPAN session, perform this task:

The following example shows creating a SPAN session:

switch# configure terminal
switch(config)# monitor session 2

To ensure that you are working with a completely new session, you can delete the desired session number or all SPAN sessions.

To delete SPAN sessions, perform this task:

Configuring the Destination Port

The SPAN destination port can only be a physical port on the switch. There are minor differences between the configuration of Ethernet and Fibre Channel destination ports as detailed in the following topics.

Configuring an Ethernet Destination Port

To configure an Ethernet interface as a SPAN destination port, perform this task:

The following example shows configuring an Ethernet SPAN destination port:

switch# configure terminal
switch(config)# interface ethernet 1/3
switch(config-if)# switchport monitor
switch(config-if)# exit
switch(config)# monitor session 2
switch(config-monitor)# destination interface ethernet 1/3

Configuring Fibre Channel Destination Port

To configure a Fibre Channel port as a SPAN destination port, perform this task:

The following example shows configuring an Ethernet SPAN destination port:

switch# configure terminal
switch(config)# interface fc 2/4
switch(config-if)# switchport mode SD
switch(config-if)# switchport speed 1000
switch(config-if)# exit
switch(config)# monitor session 2
switch(config-monitor)# destination interface fc 2/4

Configuring Source Ports

You can configure the source ports for a SPAN session. The source ports can be Ethernet, Fibre Channel, or virtual Fibre Channel ports.

To configure the source ports for a SPAN session, perform this task:

The following example shows configuring an Ethernet SPAN source port:

switch# configure terminal
switch(config)# monitor session 2
switch(config-monitor)# source interface ethernet 1/16

The following example shows configuring a Fibre Channel SPAN source port:

...
switch(config-monitor)# source interface fc 2/1

The following example shows configuring a virtual Fibre Channel SPAN source port:

...
switch(config-monitor)# source interface vfc 129

Configuring Source Port Channels, VLANs, or VSANs

You can configure the source channels for a SPAN session. These ports can be port channels, SAN port channels, VLANs, and VSANs. The monitored direction can only be ingress and applies to all physical ports in the group.

To configure the source channels for a SPAN session, perform this task:

The following example shows configuring a port channel SPAN source:

switch# configure terminal
switch(config)# monitor session 2
switch(config-monitor)# source interface port-channel 1 rx

The following example shows configuring a SAN port channel SPAN source:

...
switch(config-monitor)# source interface san-port-channel 3 rx

The following example shows configuring a VLAN SPAN source:

...
switch(config-monitor)# source vlan 1

• The following example shows configuring a VSAN SPAN source:

...
switch(config-monitor)# source vsan 1

Configuring the Description of a SPAN Session

To provide a descriptive name of the SPAN session for ease of reference, perform this task:

The following example shows configuring a description of a SPAN session:

switch# configure terminal
switch(config)# monitor session 2
switch(config-monitor)# description monitoring ports fc2/2-fc2/4

Suspending or Activating a SPAN Session

The default is to keep the session state shut. To open a session that duplicates packets from sources to destinations, perform this task:

The following example shows suspending a SPAN session:

...
switch(config)# monitor session 3 shut

To suspend a SPAN session, perform this task:

Note The Cisco Nexus 5000 Series switch supports two active SPAN sessions. When you configure more than two SPAN sessions, the first two sessions are active. During startup, the order of active sessions is reversed; the last two sessions are active. For example, if you configured ten sessions 1 to 10 where 1 and 2 are active, after a reboot, sessions 9 and 10 will be active. To enable deterministic behavior, explicitly suspend the sessions 3 to 10 with the monitor session session-number shut command.

Displaying SPAN Information

To display SPAN information, perform this task:

This example shows how to display SPAN session information:

This example shows how to display SPAN session details: