SPAN Configuration and verification on Cisco Nexus 7000

In this post, we will go briefly into the configuration of the SPAN feature on the Nexus 7K switch.

SPAN Overview

SPAN for ethernet ports monitors all traffic for the source port, which sends a copy of the traffic to a destination port. The network analyzer, which is attached to the destination port, analyzes the traffic that passes through the source port.

A Source port can be a single port or multiple ports or a VLAN, which is also called a monitored port. You can monitor:

• All the packets for the source port which is received (ingress, Rx).
• Transmitted (egress, tx)
• Bidirectional (both).

A replication of the packets from the SPAN source is sent to the SPAN destination port for analysis.

For VLAN-based SPAN (VSPAN), all ports in VLAN are source ports. So the traffic in the VLAN is monitored. You can apply VLAN based filter on the trunk port of the switch to limit the SPAN traffic monitor.

SPAN Configuration on Nexus 7000 series switches

Actually, In order to configure  Switched Port Analyzer (SPAN) on Nexus 7000 switches, 2 steps need to be done:

Step 1: Configure the destination interface as “Swichport monitor”:

interface Ethernet1/10
  description ### TO_Sniffer_Device ###
  switchport
  switchport monitor
  no shutdown
  exit

Step 2: Configure the SPAN session:

• Interface as SPAN source:

monitor session 1
  description ### SPAN_uplinks_Traffic ###
  source interface ethernet 1/1 both
  destination interface ethernet 1/10
  no shut
  exit

copy running-config startup-config

• VLANs as SPAN source:

monitor session 1
  description ### SPAN_uplinks_Traffic ###
  source vlan 10, 40-50 both
  destination interface ethernet 1/10
  no shut
  exit

copy running-config startup-config

SPAN verification on Nexus 7000 series switches

• Show monitor:

N7K-1#show monitor

Session  State        Reason                  Description
-------  -----------  ----------------------
--------------------------------
1        up           The session is up

N7K-1#show monitor session all
    
  session 1
---------------
type              : local
state             : up
source intf       :
    rx            : Eth1/1
    tx            : Eth1/1
    both          : Eth1/1
source VLANs      :
    rx            :
    tx            :
    both          :
filter VLANs      : filter not specified
destination ports : Eth1/10