17. Mirroring

17.1. Overview

Mirroring copies IPv4 and IPv6 packets seen on a specified source, such as an interface (port) or subinterface (VLAN), and sends the packets to a specific destination, such as a locally attached traffic analyzer.

By default, the mirrored packets include IPv4/IPv6 headers, as well as Ethernet headers. Traffic from multiple sources can be mirrored to a single destination, although traffic from a given source cannot be mirrored to multiple destinations.

17.2. Mirror sources

A mirror source can be an interface, including all subinterfaces within that interface. The source can be a single interface (for example, interface ethernet-1/1) or a LAG (for example, interface lag1). Either a LAG member or LAG port can be mirrored. When a LAG port is configured as a mirror source, mirroring is enabled on all ports making up the LAG.

The source can be a specific VLAN; that is, a subinterface within an interface where VLAN tagging is enabled (for example, interface ethernet-1/1.1 or lag1.1).

You can configure mirroring for traffic in a specific direction (ingress only, egress only) or bidirectional traffic (both ingress and egress).

17.3. Mirror destinations

Traffic from the mirror source can be copied to a local destination (local mirroring). In a local mirroring configuration, both the mirror source and mirror destination reside on the same SR Linux node, as shown in Figure 6.

In this configuration, the local destination is a Switched Port Analyzer (SPAN).

Figure 6:  Local mirroring 

17.4. Configuring mirroring

To configure mirroring, you enable a subinterface to be a local mirror destination, then configure a mirroring instance, which specifies the source and destination for the mirrored traffic. Multiple mirror sources can have a single destination, although traffic from a given source cannot be mirrored to multiple destinations. Only one mirror destination can be configured per mirroring instance. A mirror destination cannot be reused in multiple mirroring instances

Within a mirroring instance, if an interface is configured as mirror source, a subinterface within that interface cannot be added as another mirror source. If a LAG is defined as mirror destination, only the first 8 members of the LAG carry mirrored traffic.

Example:

The following enables a subinterface and LAG subinterface as local mirror destinations:

--{ * candidate shared default }--[  ]--
# info interface ethernet-1/4 subinterface 1
    interface ethernet-1/4 {
        subinterface 1 {
            type local-mirror-dest
            admin-state enable
        }
    }
--{ * candidate shared default }--[  ]--
# info interface lag25 subinterface 1
    interface lag25 {
        subinterface 1 {
            type local-mirror-dest
            admin-state enable
        }
    }

The following configures two mirror instances. One mirror instance configures the Ethernet interface as a mirror source and a subinterface as destination, and the other configures a LAG as mirror source and a LAG subinterface as destination.

--{ * candidate shared default }--[  ]--
# info system mirroring
    system {
        mirroring {
            mirroring-instance 1 {
                admin-state enable
                mirror-source {
                    interface ethernet-1/5 {
                        direction ingress-egress
                    }
                }
                mirror-destination {
                    local ethernet-1/4.1
                }
            }
            mirroring-instance 2 {
                admin-state enable
                mirror-source {
                    interface lag1 {
                        direction ingress-egress
                    }
                }
                mirror-destination {
                    local lag25.1
                }
            }
        }
    }

17.4.1. Displaying mirroring information

Use the info from state command to display mirroring configuration information. For example:

--{ * candidate shared default }--[  ]--
# info from state system mirroring mirroring-instance 2
    system {
        mirroring {
            mirroring-instance 2 {
                admin-state enable
                oper-state down
                oper-down-reason local-mirror-subif-down
                mirror-source {
                    interface lag1 {
                        direction ingress-egress
                    }
                }
                mirror-destination {
                    local lag25.1
                }
            }
        }
    }

17.4.2. Displaying mirroring statistics

You can use the info from state command to display the outgoing mirrored packets/octets per interface. For example:

--{ * candidate shared default }--[  ]--
# info from state interface ethernet-1/1 statistics | grep mirror
            out-mirror-octets 0
            out-mirror-packets 0