Configuring Traffic Mirroring

This module describes the configuration of the traffic mirroring feature. Traffic mirroring is sometimes called port mirroring, or switched port analyzer (SPAN).

Feature History for Traffic Mirroring

Release

Modification

Release 7.0.2

SPAN over Pseudo-Wire was introduced.

Introduction to Traffic Mirroring

Traffic mirroring, sometimes called port mirroring or Switched Port Analyzer (SPAN), is a Cisco proprietary feature that enables you to monitor network traffic passing in or out of a set of ports. You can then pass this traffic to a destination port on the same router.

Traffic mirroring copies traffic from one or more source ports and sends the copied traffic to one or more destinations for analysis by a network analyzer or other monitoring device. Traffic mirroring does not affect the flow of traffic on the source interfaces or sub-interfaces. It allows the mirrored traffic to be sent to a destination interface or sub-interface.

For example, you can attach a traffic analyzer to the router and capture Ethernet traffic that is sent by host A to host B.

Figure 1. Traffic Mirroring Operation

When local traffic mirroring is enabled, the traffic analyzer gets directly attached to the port that is configured to receive a copy of every packet that host A sends. This port is called a traffic mirroring port.


Note

  • From Release 7.2.1, traffic mirroring is introduced on Cisco NCS 5700 line cards.

  • From Release 7.4.2, you can mirror incoming (Rx) and outgoing (Tx) traffic from the source ports to separate destinations on Cisco NC57 line cards. During a session, you can configure one destination port for incoming traffic and one for outgoing traffic.

Traffic Mirroring Types

The following types of traffic mirroring are supported:

  • Local traffic mirroring: This is the most basic form of traffic mirroring. The network analyzer or sniffer is attached directly to the destination interface. In other words, all monitored ports are located on the same router as the destination port.

  • Remote traffic mirroring: The network analyzer is reached through a GRE tunnel over an IP network.


    Note

    A copy of every packet includes the Layer 2 header if the ethernet keyword is configured. As this renders the mirrored packets unroutable, the end point of the GRE tunnel must be the network analyzer.

  • ACL-based traffic mirroring: Traffic is mirrored based on the configuration of the interface ACL.

    You can mirror traffic based on the definition of an interface access control list. When you are mirroring Layer 3 traffic, the ACL is configured using the ipv4 access-list or the ipv6 access-list command with the capture option. The permit and deny commands determine the behavior of regular traffic. The capture option designates the packet is to be mirrored to the destination port, and it is supported only on permit type of access control entries (ACEs).


    Note

    Prior to Release 6.5.1, ACL-based traffic mirroring required the use of UDK (User-Defined TCAM Key) with the enable-capture option so that the capture option can be configured in the ACL.

  • Encapsulated remote SPAN (ERSPAN): ERSPAN enables generic routing encapsulation (GRE) for all captured traffic and allows it to be extended across Layer 3 domains.

  • SPAN over Pseudo-Wire: Pseudo-wire traffic mirroring (known as PW-SPAN) is an extra functionality on the existing SPAN solutions. In PW-SPAN, the traffic mirroring destination port is configured as pseudo-wire rather than a physical port. Here, the designated traffic on the source port is mirrored over the pseudo-wire to a central location.

  • SPAN to File: SPAN to File is an extension of the pre-existing SPAN feature that allows network packets to be mirrored to a file instead of an interface. This helps in the analysis of the packets at a later stage.

  • File Mirroring: File mirroring feature enables the router to copy files or directories automatically from /harddisk:/mirror location in active RP to /harddisk:/mirror location in standby RP or RSP without user intervention or EEM scripts.

Traffic Mirroring Terminology

  • Ingress Traffic — Traffic that comes into the router.

  • Egress Traffic — Traffic that goes out of the router.

  • Source (SPAN) interface — An interface that is monitored using the SPAN feature.

  • Source port—A port that is monitored with the use of traffic mirroring. It is also called a monitored port.

  • Destination port—A port that monitors source ports, usually where a network analyzer is connected. It is also called a monitoring port.

  • Monitor session—A designation for a collection of SPAN configurations consisting of a single destination and, potentially, one or many source interfaces.

Characteristics of Source Port

A source port, also called a monitored port, is a routed port that you monitor for network traffic analysis. In a single traffic mirroring session, you can monitor source port traffic. The Cisco NCS 5500 Series Routers support a maximum of up to 800 source ports.

A source port has these characteristics:

  • It can be any data port type, such as Bundle Interface, 100 Gigabit Ethernet, or 10 Gigabit Ethernet.


    Note

    Bridge group virtual interfaces (BVIs) are not supported.

  • Each source port can be monitored in only one traffic mirroring session.

  • When a port is used as a source port, the same port cannot be used as a destination port.

  • Each source port can be configured with a direction (ingress, egress, or both) to monitor local traffic mirroring. Remote traffic mirroring is supported both in the ingress and egress directions. For bundles, the monitored direction applies to all physical ports in the group.

Characteristics of Destination Port

Each session must have a destination port that receives a copy of the traffic from the source ports.

A destination port has these characteristics:

  • A destination port must reside on the same router as the source port for local traffic mirroring. For remote mirroring, the destination is always a GRE tunnel.

  • A destination port for local mirroring can be any Ethernet physical port, EFP, GRE tunnel interface, or bundle interface. It can be a Layer 2 or Layer 3 transport interface.

  • At any one time, a destination port can participate in only one traffic mirroring session. 
A destination port in one traffic mirroring session cannot be a destination port for a second traffic mirroring session. In other words, no two monitor sessions can have the same destination port.

  • A destination port cannot also be a source port.

Characteristics of Monitor Session

A monitor session is a collection of traffic mirroring configurations consisting of a single destination and, potentially, many source interfaces. For any given monitor session, the traffic from the source interfaces (called source ports) is sent to the monitoring port or destination port. If there are more than one source port in a monitoring session, the traffic from the several mirrored traffic streams is combined at the destination port. The result is that the traffic that comes out of the destination port is a combination of the traffic from one or more source ports.

Monitor sessions have these characteristics:

  • A single router can have a maximum of four monitor sessions. However, both SPAN and CFM share common mirror profiles. If you configure SPAN and CFM together on the router, the maximum number of monitor sessions may reduce to two.

  • Cisco NC57 line cards support only four Rx and three Tx monitor sessions.

  • A single monitor session can have only one destination port.

  • A single destination port can belong to only one monitor session.

  • A monitor session can have a maximum of 800 source ports, as long as the maximum number of source ports from all monitoring sessions does not exceed 800.

Restrictions

Generic Restrictions

The following are the generic restriction(s) related to traffic mirroring:

  • Partial mirroring and sampled mirroring are not supported.

  • Sub-interface configured as source interface is not supported on SPAN.

  • The destination bundle interfaces flap when:

    • both the mirror source and destination are bundle interfaces in LACP mode and

    • mirror packets next-hop is a router or a switch instead of a traffic analyzer.

    This behavior is observed due to a mismatch of LACP packets on the next-hop bundle interface due to the mirroring of LACP packets on the source bundle interface.

  • Both SPAN and ERSPAN features cannot be configured on a router simultaneously. Either SPAN or ERSPAN feature can be configured on the same router.

SPAN Restrictions

The following restrictions apply to SPAN:

  • SPAN only supports port-level source interfaces.

ERSPAN Restrictions

The following restrictions apply to ERSPAN:

  • The value of ERSPAN session-ID is always zero. IOS XR Command for configuring ERPAN is not available.

  • ERSPAN next-hop must have ARP resolved. Any other traffic or protocol will trigger ARP.

  • ERSPAN cannot travel over MPLS.

    • Additional routers may encapsulate in MPLS.

  • ERSPAN decapsulation is not supported.

  • ERSPAN does not work if the GRE next hop is reachable over sub-interface. For ERSPAN to work, the next hop must be reachable over the main interface.

SPAN-ACL Restrictions

The following restrictions apply to SPAN-ACL:

  • SPAN-ACL is only supported in the Rx direction, that is, in the ingress direction v4 or v6 ACL.

  • MPLS traffic cannot be captured with SPAN-ACL.

    • ACL for any MPLS traffic is not supported.

Configure Traffic Mirroring

These tasks describe how to configure traffic mirroring:

Configure Remote Traffic Mirroring

Procedure

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2

monitor-session session-name

Example:


RP/0/RP0/CPU0:router(config)# monitor-session mon1 ethernet
RP/0/RP0/CPU0:router(config-mon)#

Defines a monitor session and enters monitor session configuration mode.

Step 3

destination interface tunnel-ip

Example:


RP/0/RP0/CPU0:router(config-mon)# destination interface tunnelip3

Specifies the destination subinterface to which traffic is replicated.

Step 4

exit

Example:


RP/0/RP0/CPU0:router(config-mon)# exit
RP/0/RP0/CPU0:router(config)#

Exits monitor session configuration mode and returns to global configuration mode.

Step 5

interface type number

Example:


RP/0/RP0/CPU0:router(config)# interface HundredGigE 0/1/0/1

Enters interface configuration mode for the specified source interface. The interface number is entered in rack /slot /module /port notation. For more information about the syntax for the router, use the question mark (?) online help function.

Step 6

monitor-session session-name ethernet direction rx-onlyport-only

Example:


RP/0/RP0/CPU0:router(config-if)# monitor-session mon1 ethernet 
direction rx-only port-only

Specifies the monitor session to be used on this interface. Use the direction keyword to specify that only ingress or egress traffic is mirrored.

Step 7

end or commit

Example:


RP/0/RP0/CPU0:router(config-if)# end

or 


RP/0/RP0/CPU0:router(config-if)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting (yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 8

show monitor-session [session-name] status [detail] [error]

Example:


RP/0/RP0/CPU0:router# show monitor-session

Displays information about the traffic mirroring session.

Example

This example shows the basic configuration for traffic mirroring with physical interfaces.
RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# monitor-session ms1
RP/0/RP0/CPU0:router(config-mon)# destination interface HundredGigE0/2/0/15
RP/0/RP0/CPU0:router(config-mon)# commit
RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# interface TenGigE0/2/0/19
RP/0/RP0/CPU0:router(config-if)# monitor-session ms1 ethernet direction rx-only port-level
RP/0/RP0/CPU0:router(config-if)# commit

This example shows sample output of the show monitor-session command with the status keyword:

RP/0/RSP0/CPU0:router# show monitor-session status
Monitor-session cisco-rtp1
Destination interface HundredGigE 0/5/0/38
================================================================================
Source Interface Dir Status
--------------------- ---- ----------------------------------------------------
TenGigE0/5/0/4 Both Operational
TenGigE0/5/0/17 Both Operational
RP/0/RSP0/CPU0:router# show monitor-session status detail
Monitor-session sess1
Destination interface is not configured
Source Interfaces
-----------------
TenGigE0/1/0/0
Direction: Both
ACL match: Disabled
Portion: Full packet
Status: Not operational (destination interface not known).
TenGigE0/1/0/1
Direction: Both
ACL match: Disabled
Portion: First 100 bytes

RP/0/RSP0/CPU0:router# show monitor-session status error
Monitor-session ms1
Destination interface TenGigE0/2/0/15 is not configured
================================================================================
Source Interface Dir Status
--------------------- ---- ----------------------------------------------------
Monitor-session ms2
Destination interface is not configured
================================================================================
Source Interface Dir Status
--------------------- ---- ----------------------------------------------------
RP/0/RP0/CPU0:router# show monitor-session test status
Monitor-session test (ipv4)
Destination Nexthop 255.254.254.4
=========================================================================================
Source Interface Dir Status
-----------------------------------------------------------------------------------------
Gi0/0/0/2.2 Rx Not operational (source same as destination)
Gi0/0/0/2.3 Rx Not operational (Destination not active)
Gi0/0/0/2.4 Rx Operational
Gi0/0/0/4 Rx Error: see detailed output for explanation
RP/0/RP0/CPU0:router# show monitor-session test status error
Monitor-session test
Destination Nexthop ipv4 address 255.254.254.4
===============================================================
Source Interface Status
---------------------------------------------------------------
Gi0/0/0/4 < Error: FULL Error Details >

Configuring ACLs for Traffic Mirroring

This section describes the configuration for creating ACLs for traffic mirroring.

In ACL-based traffic mirroring, traffic is mirrored based on the configuration of the interface ACL. You can mirror traffic based on the definition of an interface access control list. When you are mirroring Layer 3 or Layer 2 traffic, the ACL is configured using the ipv4 access-list or the ipv6 access-list command with the capture option. The permit and deny commands determine the behavior of regular traffic.

Guidelines and Restrictions

The following general restrictions apply to traffic mirroring using ACLs:

  • Traffic mirroring counters are not supported.

  • ACL-based traffic mirroring is not supported with Layer 2 (ethernet-services) ACLs.

  • Configure ACL(s) on the source interface or any interface on the same network processing unit as the source interface, to avoid default mirroring of traffic. If a Bundle interface is a source interface, configure the ACL(s) on any interface on the same network processing unit as all active bundle-members. Bundle members can be on multiple NPUs. Also ensure that the ACL(s) configured are of the same protocol type and direction as the SPAN configuration. For example, if you configure SPAN with ACL for IPv4 or IPv6, configure an ingress IPv4 or IPv6 ACL on that network processing unit respectively.

Configuring an IPv4 ACL

Use the following steps to configure ACLs for traffic mirroring.

/* Create an IPv4 ACL (TM-ACL) for traffic mirroring */ 
Router(config)# ipv4 access-list TM-ACL 
Router(config-ipv4-acl)# 10 permit udp 10.1.1.0 0.0.0.255 eq 10 any capture
Router(config-ipv4-acl)# 20 permit udp 10.1.1.0 0.0.0.255 eq 20 any 
Router(config-ipv4-acl)# exit
Router(config)# commit 

/* Validate the configuration */
Router(config)# show run
Thu May 17 11:17:49.968 IST
Building configuration...
!! IOS XR Configuration 0.0.0
!! Last configuration change at Thu May 17 11:17:47 2018 by user
…
ipv4 access-list TM-ACL
 10 permit udp 10.1.1.0 0.0.0.255 eq 10 any capture
 20 permit udp 10.1.1.0 0.0.0.255 eq 20 any
!
…

You have successfully configured an IPv4 ACL for traffic mirroring.

Attaching the Configurable Source Interface

Procedure

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2

interface type number

Example:


RP/0/RP0/CPU0:router(config)# interface HundredGigE 0/1/0/1

Enters interface configuration mode for the specified source interface. The interface number is entered in rack /slot /module /port notation. For more information about the syntax for the router, use the question mark (?) online help function.

Step 3

ipv4 access-group acl-name {ingress | egress}

Example:


RP/0/RP0/CPU0:router(config-if)# ipv4 access-group acl1 ingress

Controls access to an interface.

Step 4

monitor-session session-name ethernet direction rx-onlyport-level acl

Example:


RP/0/RP0/CPU0:router(config-if)# monitor-session mon1 ethernet direction rx-only port-level acl
RP/0/RP0/CPU0:router(config-if-mon)#

Attaches a monitor session to the source interface and enters monitor session configuration mode.

Note 

rx-only specifies that only ingress traffic is replicated.

Step 5

acl

Example:


RP/0/RP0/CPU0:router(config-if-mon)# acl

Specifies that the traffic mirrored is according to the defined ACL.

Note 

If an ACL is configured by name, then this step overrides any ACL that may be configured on the interface.

Step 6

exit

Example:


RP/0/RP0/CPU0:router(config-if-mon)# exit
RP/0/RP0/CPU0:router(config-if)#

Exits monitor session configuration mode and returns to interface configuration mode.

Step 7

end or commit

Example:


RP/0/RP0/CPU0:router(config-if)# end

or 


RP/0/RP0/CPU0:router(config-if)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting (yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 8

show monitor-session [session-name] status [detail] [error]

Example:


RP/0/RP0/CPU0:router# show monitor-session status

Displays information about the monitor session.

Configuring UDF-Based ACL for Traffic Mirroring

Procedure

  Command or Action Purpose

Step 1

configure

Example:


RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2

udf udf-name header {inner | outer} {l2 | l3 | l4} offset offset-in-bytes length length-in-bytes

Example:


RP/0/RP0/CPU0:router(config)# udf udf3 header outer l4 offset 0 length 1
(config-mon)#

Example:


RP/0/RP0/CPU0:router(config)# udf udf3 header inner l4 offset 10 length 2 
(config-mon)#

Example:


RP/0/RP0/CPU0:router(config)# udf udf3 header outer l4 offset 50 length 1
(config-mon)#

Configures individual UDF definitions. You can specify the name of the UDF, the networking header from which offset, and the length of data to be extracted.

The inner or outer keywords indicate the start of the offset from the unencapsulated Layer 3 or Layer 4 headers, or if there is an encapsulated packet, they indicate the start of offset from the inner L3/L4.

Note 

The maximum offset allowed, from the start of any header, is 63 bytes

The length keyword specifies, in bytes, the length from the offset. The range is from 1 to 4.

Step 3

ipv4 access-list acl-name

Example:


RP/0/RP0/CPU0:router(config))# ipv4 access-list acl1

Creates ACL and enters IP ACL configuration mode. The length of the acl-name argument can be up to 64 characters.

Step 4

permit regular-ace-match-criteria udf udf-name1 value1 ... udf-name8 value8

Example:


RP/0/RP0/CPU0:router(config-ipv4-acl)# 10 permit ipv4 any any udf udf1 0x1234 0xffff udf3 0x56 0xff capture
RP/0/RP0/CPU0:router(config-ipv4-acl)# 30 permit ipv4 any any dscp af11 udf udf5 0x22 0x22 capture

Configures ACL with UDF match.

Step 5

exit

Example:


RP/0/RP0/CPU0:router(config-ipv4-acl)# exit

Exits IP ACL configuration mode and returns to global configuration mode.

Step 6

interfacetype number

Example:


RP/0/RP0/CPU0:router(config)# interface HundredGigE 0/2/0/2

Configures interface and enters interface configuration mode.

Step 7

ipv4 access-group acl-name ingress

Example:


RP/0/RP0/CPU0:router(config-if)# ipv4 access-group acl1 ingress

Applies access list to an interface.

Step 8

commit

Example:


RP/0/RP0/CPU0:router(config-if)# commit

Applies access list to an interface.

Verifying UDF-based ACL

Use the show monitor-session status detail command to verify the configuration of UDF on ACL. 

RP/0/RP0/CPU0:leaf1# show monitor-session 1 status detail 

Fri May 12 19:40:39.429 UTC
Monitor-session 1
  Destination interface tunnel-ip3
  Source Interfaces
  -----------------
  TenGigE0/0/0/15
    Direction:  Rx-only
    Port level: True
    ACL match:  Enabled
    Portion:    Full packet
    Interval:   Mirror all packets
    Status:     Not operational (destination not active)

Traffic Mirroring on Layer 2 Interfaces

Monitoring Traffic Mirroring on a Layer 2 Interface

This section describes the configuration for monitoring traffic on a Layer 2 interface.

Configuration

To monitor traffic mirroring on a Layer 2 interface, configure the monitor under l2transport sub-config of the interface: 

RP/0/RP0/CPU0:router(config)# interface TenGigE0/0/0/42
RP/0/RP0/CPU0:router(config-if)# l2transport
RP/0/RP0/CPU0:router(config-if-l2)# monitor-session EASTON ethernet port-level

Verification

RP/0/RP0/CPU0:router# show monitor-session status 
Thu Aug 29 21:42:22.829 UTC
Monitor-session EASTON
Destination interface TenGigE0/0/0/20
=============================================
Source Interface      Dir   Status
--------------------- ----  -----------------
Te0/0/0/42 (port)     Both  Operational

ERSPAN

Encapsulated Remote Switched Port Analyzer (ERSPAN) transports mirrored traffic over an IP network. The traffic is encapsulated at the source router and is transferred across the network. The packet is decapsulated at the destination router and then sent to the destination interface.

ERSPAN involves mirroring traffic through a GRE tunnel to a remote site. For more information on configuring the GRE tunnel that is used as the destination for the monitor sessions, see the chapter Configuring GRE Tunnels.

Monitor Multiple ERSPAN Sessions with SPAN and Security ACL

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Monitor Multiple ERSPAN Sessions with SPAN and Security ACL

 Release 7.5.4

With this feature, you can use SPAN and security ACL together to monitor multiple ERSPAN sessions under the same source interface. SPAN ACL helps you to distribute the mirrored traffic over different destination interfaces and Security ACL helps you to allow selective incoming traffic.

The SPAN and security ACLs are applicable only in the ingress traffic.

Configure Multiple ERSPAN monitor Sessions with SPAN and Security ACL

Running configuration

Router(config)#show running-config interface
monitor-session always-on-v4 ethernet direction rx-only port-level
  acl ipv4 v4-monitor-acl2
  acl ipv6 v6-monitor-acl2
!
monitor-session on-demand-v4 ethernet direction rx-only port-level
  acl ipv4 v4-monitor-acl2
  acl ipv6 v6-monitor-acl2
!
ipv4 access-group sec_aclv4 ingress
ipv6 access-group sec_aclv6 ingress
!
!

Introduction to ERSPAN Egress Rate Limit

With ERSPAN egress rate limit feature, you can monitor traffic flow through any IP network. This includes third-party switches and routers.

ERSAPN operates in the following modes:

  • ERSPAN Source Session – box where the traffic originates (is SPANned).

  • ERSPAN Termination Session or Destination Session – box where the traffic is analyzed.

This feature provides rate limiting of the mirroring traffic or the egress traffic. With rate limiting, you can limit the amount of egress traffic to a specific rate, which prevents the network and remote ERSPAN destination traffic overloading. Be informed, if the egress rate-limit exceeds then the system may cap or drop the monitored traffic.

You can configure the QoS parameters on the traffic monitor session.

  • Traffic Class (0 through 7)

    • Traffic class 0 has the lowest priority and 7 the highest.

    • The default traffic class is the same as that of the original traffic class.

  • The Discard Class (0 through 2):

    • The default is 0.

    • The discard class configuration is used in WRED.

Benefits

With ERSPAN Egress rate limit feature, you can limit the egress traffic or the mirrored and use the mirrored traffic for data analysis.

Topology

Figure 2. Topology for ERSPAN Egress Rate Limit

The encapsulated packet for ERSPAN is in ARPA/IP format with GRE encapsulation. The system sends the GRE tunneled packet to the destination box identified by an IP address. At the destination box, SPAN-ASIC decodes this packet and sends out the packets through a port. ERSPAN egress rate limit feature is applied on the router egress interface to rate limit the monitored traffic.

The intermediate switches carrying ERSPAN traffic from source session to termination session can belong to any L3 network.

Configure ERSPAN Egress Rate Limit

Use the following steps to configure ERSPAN egress rate limit:

monitor-session ERSPAN ethernet
destination interface tunnel-ip1
!
RP/0/RP0/CPU0:pyke-008#sh run int tunnel-ip 1
interface tunnel-ip1
ipv4 address 4.4.4.1 255.255.255.0
tunnel mode gre ipv4
tunnel source 20.1.1.1
tunnel destination 20.1.1.2
!

RP/0/RP0/CPU0:pyke-008#sh run int hundredGigE 0/0/0/16

interface HundredGigE0/0/0/16
ipv4 address 215.1.1.1 255.255.255.0
ipv6 address 3001::2/64
monitor-session ERSPAN ethernet direction rx-only port-level
  acl
!
ipv4 access-group ACL6 ingress

Running Configuration

!! Policy-map to be used with the ERSPAN Destination (egress interface)
!! Traffic class is set to 5. For packets in this class, apply shaping
!! as well as WRED.
class-map match-any TC5
 match traffic-class 5 
 end-class-map
! 
policy-map shape-foo
 class TC5
  random-detect discard-class 0 10000 bytes 40000 bytes 
  random-detect discard-class 1 40000 bytes 80000 bytes 
  random-detect discard-class 2 80000 bytes 200000 bytes 
  shape average percent 15 
 !  
 class class-default
 ! 
 end-policy-map
! 
!!GRE Tunnel Interface
interface Loopback49
 ipv4 address 49.49.49.49 255.255.255.255
!
interface tunnel-ip100
 ipv4 address 130.100.1.1 255.255.255.0
 tunnel mode gre ipv4
 tunnel source 49.49.49.49
 tunnel destination 10.8.1.2
!
!!ERSPAN Monitor Session with GRE tunnel as the Destination Interface, and with QoS configuration
monitor-session FOO ethernet
 destination interface tunnel-ip100
 traffic-class 5
 discard-class 1
!
!!ERSPAN Source Interface
interface TenGigE0/6/0/4/0
 description connected to TGEN 9/5
 ipv4 address 10.4.90.1 255.255.255.0
 monitor-session FOO ethernet port-level
 !
!
!!ERSPAN Destination ip-tunnel00’s underlying interface, with egress policy-map shape-foo attached
interface TenGigE0/6/0/9/0
 service-policy output shape-foo
 ipv4 address 10.8.1.1 255.255.255.0

Verification

RP/0/RP0/CPU0:ios#show monitor-session FOO status detail   
Wed May  2 15:14:05.762 UTC
Monitor-session FOO
  Destination interface tunnel-ip100
  Source Interfaces
  -----------------
  TenGigE0/6/0/4/0
    Direction:  Both
    Port level: True
    ACL match:  Disabled
    Portion:    Full packet
    Interval:   Mirror all packets
    Status:     Operational
RP/0/RP0/CPU0:ios#
show monitor-session <sess-id> status internal

RP/0/RP0/CPU0:ios#show monitor-session FOO status internal 
Wed May  2 15:13:06.063 UTC
Information from SPAN Manager and MA on all nodes:
Monitor-session FOO (ID 0x00000001) (Ethernet)
SPAN Mgr: Destination interface tunnel-ip100 (0x0800001c)
          Last error: Success
          Tunnel data:
            Mode: GREoIPv4
            Source IP: 49.49.49.49
            Dest IP: 10.8.1.2
            VRF: 
            ToS: 0 (copied)
            TTL: 255
            DFbit: Not set
0/6/CPU0: Destination interface tunnel-ip100 (0x0800001c)
          Tunnel data:
            Mode: GREoIPv4
            Source IP: 49.49.49.49
            Dest IP: 10.8.1.2
            VRF: 
            ToS: 0 (copied)
            TTL: 255
            DFbit: Not set

Information from SPAN EA on all nodes:
Monitor-session 0x00000001 (Ethernet)
0/6/CPU0: Name 'FOO', destination interface tunnel-ip100 (0x0800001c)
Platform, 0/6/CPU0:

  Dest Port: 0xe7d

  ERSPAN Encap:
    Tunnel ID: 0x4001380b
    ERSPAN Tunnel ID: 0x4001380c
    IP-NH Grp key: 0x3140000cc5
    IP-NH hdl: 0x308a5fa5e0
    IP-NH IFH: 0x30002a0
    IP-NH IPAddr: 10.4.91.2

  NPU   MirrorRx     MirrorTx    
  00    0x00000003   0x00000004
  01    0x00000003   0x00000004
  02    0x00000003   0x00000004
  03    0x00000003   0x00000004
  04    0x00000003   0x00000004
  05    0x00000003   0x00000004
RP/0/RP0/CPU0:ios#

SPAN

SPAN over Pseudo-Wire

Pseudo-wire traffic mirroring (known as PW-SPAN) is an extra functionality on the existing SPAN solutions. The existing SPAN solutions are monitored on a destination interface or through a GRE tunnel or RSPAN. In PW-SPAN, the traffic mirroring destination port is configured to be a pseudo-wire rather than a physical port. Here, the designated traffic on the source port is mirrored over the pseudo-wire to a central location. This allows the centralization of expensive network traffic analysis tools.

Because the pseudo-wire carries only mirrored traffic, this traffic is unidirectional. Incoming traffic from the remote provider edge is not allowed. Typically, a monitor session should be created with a destination pseudo-wire. This monitor session is one of the L2VPN xconnect segments. The other segment of the L2VPN VPWS is a pseudowire.


Note

  • A single router can have a maximum of four monitor sessions.

  • Only port-level source interfaces are supported.

Limitations

The following functionalities are not supported for SPAN over PW:

  • Monitor session statistics

  • RSPAN

  • Partial packet SPAN

  • Sampled SPAN

  • ERSPAN Tunnel statistics

  • A destination port cannot be a source port.

Configuring SPAN over Pseudo-Wire

Use the following steps to configure SPAN over Pseudo-Wire:

Configure SPAN monitor session 

RP/0/RP0/CPU0:router#config
RP/0/RP0/CPU0:router(config)#monitor-session M1
RP/0/RP0/CPU0:router(config-mon)#destination pseudowire 
RP/0/RP0/CPU0:router(config-mon)#commit

Configure SPAN source 

RP/0/RP0/CPU0:router#config
Fri Sep  6 03:49:59.312 UTC
RP/0/RP0/CPU0:router(config)#interface Bundle-Ether100
RP/0/RP0/CPU0:router(config-if)#monitor-session M1 ethernet port-level
RP/0/RP0/CPU0:router(config-if-mon)#commit

Configure l2vpn xconnect 

RP/0/RP0/CPU0:router(config)#l2vpn
RP/0/RP0/CPU0:router(config-l2vpn)#pw-class span
RP/0/RP0/CPU0:router(config-l2vpn-pwc)#encapsulation mpls
RP/0/RP0/CPU0:router(config-l2vpn-pwc-mpls)#transport-mode ethernet
RP/0/RP0/CPU0:router(config-l2vpn)#xconnect group 1
RP/0/RP0/CPU0:router(config-l2vpn-xc)#p2p 2
RP/0/RP0/CPU0:router(config-l2vpn-xc-p2p)#monitor-session M1              
RP/0/RP0/CPU0:router(config-l2vpn-xc-p2p)#neighbor ipv4 10.10.10.1 pw-id 2
RP/0/RP0/CPU0:router(config-l2vpn-xc-p2p)#commit

Verifying SPAN over Pseudo-Wire

The following examples show how to verify SPAN over Pseudo-Wire.

To check monitor session status:

RP/0/RP0/CPU0:router#show run monitor-session M1           
monitor-session M1 ethernet
 destination pseudowire

RP/0/RP0/CPU0:router#show monitor-session M1 status        
Monitor-session M1
Destination pseudowire 
Source Interface      Dir   Status
BE100 (port)          Both  Operational
BE400 (port)          Both  Operational

RP/0/RP0/CPU0:router#show monitor-session M1 status detail 
Monitor-session M1
  Destination pseudowire 
  Source Interfaces
  -----------------
  Bundle-Ether100
    Direction:  Both
    Port level: True
    ACL match:  Disabled
    Portion:    Full packet
    Interval:   Mirror all packets
    Status:     Operational
  Bundle-Ether400
    Direction:  Both
    Port level: True
    ACL match:  Disabled
    Portion:    Full packet
    Interval:   Mirror all packets
    Status:     Operational

To check underlying l2vpn xconnect:

RP/0/RP0/CPU0:router#show run l2vpn 
l2vpn
 pw-class span
  encapsulation mpls
   transport-mode ethernet
  !
  !
  p2p 2
   monitor-session M1
   neighbor ipv4 10.10.10.1 pw-id 2
   !
  !
  p2p 10
   monitor-session M2
   neighbor ipv4 10.10.10.1 pw-id 10
    pw-class span
   !
  !
 !
!
RP/0/RP0/CPU0:router#show l2vpn xconnect 
Fri Sep  6 03:41:15.691 UTC
Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,
        SB = Standby, SR = Standby Ready, (PP) = Partially Programmed

XConnect                   Segment 1                       Segment 2                
Group      Name       ST   Description            ST       Description            ST    
------------------------   -----------------------------   -----------------------------
1          2          UP   M1                     UP       10.10.10.1         2      UP    
----------------------------------------------------------------------------------------
1          10         UP   M2                     UP       10.10.10.1         10     UP    
----------------------------------------------------------------------------------------

To verify traffic:

RP/0/RP0/CPU0:router#show controllers npu voq-usage interface tenGigE 0/0/0/12 instance all location 0/0/CPU0 
Tue Jul 16 14:06:45.040 UTC

-------------------------------------------------------------------
Node ID: 0/0/CPU0
Intf         Intf     NPU NPU  PP   Sys   VOQ   Flow   VOQ    Port 
name         handle    #  core Port Port  base  base   port   speed
             (hex)                                     type        
----------------------------------------------------------------------
Te0/0/0/12   1d0       0   0   30    30   1200  11448 local    10G

RP/0/RP0/CPU0:router#show controllers fia diagshell 0 "diag last core=0" location 0/0/CPU0 
Tue Jul 16 14:11:19.124 UTC

Node ID: 0/0/CPU0

Core 0:

Last packet information: is_valid=1  tm_port=30
pp_port=30  src_syst_port=49153  port_header_type=eth packet_size=0
Packet start, offset in bytes:
00bc6016 64db7ae7 4f59b241 884705dc 91ff7ae7 4f59b048 00109400 000286dd
60000000 00463bff 10000000 00000000 00000000 00000002 20000000 00000000
00000000 00000002 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00008a47 c35c7674

Troubleshooting Traffic Mirroring

When you encounter any issue with traffic mirroring, begin troubleshooting by checking the output of the show monitor-session status command. This command displays the recorded state of all sessions and source interfaces: 


# show monitor-session status
Monitor-session 5
rx destination interface tunnel-ip5
tx destination is not specified
================================================================================
Source Interface  Dir  Status
--------------------- ---- ----------------------------------------------------
Te0/0/0/23 (port) Rx   Operational

In the preceding example, the line marked as <Session status> can indicate one of these configuration errors:

Session Status

Explanation

Session is not configured globally

The session does not exist in global configuration. Review the show run command output and ensure that a session with a correct name has been configured.

Destination interface <intf> (<down-state>)

The destination interface is not in Up state in the Interface Manager. You can verify the state using the show interfaces command. Check the configuration to determine what might be keeping the interface from coming up (for example, a sub-interface needs to have an appropriate encapsulation configured).

The <Source interface status> can report these messages:

Source Interface Status

Explanation

Operational

Everything appears to be working correctly in traffic mirroring PI. Please follow up with the platform teams in the first instance, if mirroring is not operating as expected.

Not operational (Session is not configured globally)

The session does not exist in global configuration. Check the show run command output to ensure that a session with the right name has been configured.

Not operational (destination not known)

The session exists, but it either does not have a destination interface specified, or the destination interface named for the session does not exist. For example, if the destination is a sub-interface that has not been created.

Not operational (source same as destination)

The session exists, but the destination and source are the same interface, so traffic mirroring does not work.

Not operational (destination not active)

The destination interface or pseudowire is not in the Up state. See the corresponding Session status error messages for suggested resolution.

Not operational (source state <down-state>)

The source interface is not in the Up state. You can verify the state using the show interfaces command. Check the configuration to see what might be keeping the interface from coming up (for example, a sub-interface needs to have an appropriate encapsulation configured).

Error: see detailed output for explanation

Traffic mirroring has encountered an error. Run the show monitor-session status detail command to display more information.

The show monitor-session status detail command displays full details of the configuration parameters and any errors encountered. For example:

RP/0/RP0/CPU0:router show monitor-session status detail 


Monitor-session sess1
 Destination interface is not configured
 Source Interfaces
 -----------------
 TenGigE0/0/0/1
  Direction: Both
  ACL match: Disabled
  Portion:  Full packet
  Status:  Not operational (destination interface not known)
 TenGigE0/0/0/2
  Direction: Both
  ACL match: Disabled
  Portion:  First 100 bytes
  Status: Not operational (destination interface not known). Error: 'Viking SPAN PD' detected the 'warning' condition 'PRM connection 
          creation failure'.
Monitor-session foo
 Destination next-hop TenGigE 0/0/0/0
 Source Interfaces
 -----------------
 TenGigE 0/1/0/0.100:
  Direction: Both
  Status:  Operating
 TenGigE 0/2/0/0.200:
  Direction: Tx
  Status:  Error: <blah>

Monitor session bar
 No destination configured
 Source Interfaces
 -----------------
 TenGigE 0/3/0/0.100:
  Direction: Rx
  Status:  Not operational(no destination)

Here are additional trace and debug commands: 


RP/0/RP0/CPU0:router# show monitor-session platform trace ?

 all   Turn on all the trace
 errors Display errors
 events Display interesting events

RP/0/RP0/CPU0:router# show monitor-session trace ?

 process Filter debug by process

RP/0/RP0/CPU0:router# debug monitor-session platform ?

 all   Turn on all the debugs
 errors VKG SPAN EA errors
 event  VKG SPAN EA event
 info  VKG SPAN EA info

RP/0/RP0/CPU0:router# debug monitor-session process all

RP/0/RP0/CPU0:router# debug monitor-session process ea

RP/0/RP0/CPU0:router# debug monitor-session process ma

RP/0/RP0/CPU0:router# show monitor-session process mgr

 detail  Display detailed output
 errors  Display only attachments which have errors
 internal Display internal monitor-session information
 |     Output Modifiers

RP/0/RP0/CPU0:router# show monitor-session status

RP/0/RP0/CPU0:router# show monitor-session status errors

RP/0/RP0/CPU0:router# show monitor-session status internal