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Configuring Port Mirroring for Multiple Destinations

 

Understanding Layer 2 Port Mirroring to Multiple Destinations Using Next-Hop Groups

On an MX Series router and on an EX Series switch, you can mirror traffic to multiple destinations by configuring next-hop groups in Layer 2 port-mirroring firewall filters applied to tunnel interfaces. The mirroring of packets to multiple destinations is also known as multipacket port mirroring,

Note

Junos OS Release 9.5 introduced support for Layer 2 port mirroring using next-hop groups on MX Series routers, but required installation of a Tunnel PIC. Beginning in Junos OS Release 9.6, Layer 2 port mirroring using next-hop groups on MX Series routers does not require Tunnel PICs.

On MX Series routers and on EX Series switches, you can define a firewall filter for mirroring packets to a next-hop group. The next-hop group can contain Layer 2 members, Layer 3 members, and subgroups that are either unit list (mirroring packets to each interface) or load-balanced (mirroring packets to one of several interfaces). The MX Series router and the EX Series switch supports up to 30 next-hop groups. Each next-hop group supports up to 16 next-hop addresses. Each next-hop group must specify at least two addresses.

To enable port mirroring to the members of a next-hop group, you specify the next-hop group as the filter action of a firewall filter, and then you apply the firewall filter to logical tunnel interfaces (lt-) or virtual tunnel interfaces (vt-) on the MX Series router or on the EX Series switch.

Note

The use of subgroups for load-balancing mirrored traffic is not supported.

Defining a Next-Hop Group on MX Series Routers for Port Mirroring

Starting with release 14.2, on routers containing an Internet Processor II application-specific integrated circuit (ASIC) or T Series Internet Processor, you can send a copy of an IP version 4 (IPv4) or IP version 6 (IPv6) packet from the router to an external host address or a packet analyzer for analysis. This is known as port mirroring.

Port mirroring is different from traffic sampling. In traffic sampling, a sampling key based on the IPv4 header is sent to the Routing Engine. There, the key can be placed in a file, or cflowd packets based on the key can be sent to a cflowd server. In port mirroring, the entire packet is copied and sent out through a next-hop interface.

You can configure simultaneous use of sampling and port mirroring, and set an independent sampling rate and run-length for port-mirrored packets. However, if a packet is selected for both sampling and port mirroring, only one action can be performed, and port mirroring takes precedence. For example, if you configure an interface to sample every packet input to the interface and a filter also selects the packet to be port mirrored to another interface, only the port mirroring takes effect. All other packets not matching the explicit filter port-mirroring criteria continue to be sampled when forwarded to their final destination.

Next-hop groups allow you to include port mirroring on multiple interfaces.

On MX Series routers, you can mirror tunnel interface input traffic to multiple destinations. To this form of multipacket port mirroring, you specify two or more destinations in a next-hop group, define a firewall filter that references the next-hop group as the filter action, and then apply the filter to a logical tunnel interface lt-) or virtual tunnel interfaces (vt- on the MX Series router.

To define a next-hop group for a Layer 2 port-mirroring firewall filter action:

  1. Enable the configuration of forwarding options.
  2. Enable configuration of a next-hop-group for Layer 2 port mirroring.
  3. Specify the type of addresses to be used in the next-hop group configuration.
  4. Specify the interfaces of the next-hop route.

    or

    The MX Series router supports up to 30 next-hop groups. Each next-hop group supports up to 16 next-hop addresses. Each next-hop group must specify at least two addresses. The next-hop-address can be an IPv4 or IPv6 address.

  5. (Optional) Specify the next-hop subgroup.
  6. Verify the configuration of the next-hop group.

Example: Configuring Multiple Port Mirroring with Next-Hop Groups on M, MX and T Series Routers

When you need to analyze traffic containing more than one packet type, or you wish to perform multiple types of analysis on a single type of traffic, you can implement multiple port mirroring and next-hop groups. You can make up to 16 copies of traffic per group and send the traffic to next-hop group members. A maximum of 30 groups can be configured on a router at any given time. The port-mirrored traffic can be sent to any interface, except aggregated SONET/SDH, aggregated Ethernet, loopback (lo0), or administrative (fxp0) interfaces. To send port-mirrored traffic to multiple flow servers or packet analyzers, you can use the next-hop-group statement at the [edit forwarding-options] hierarchy level.

Figure 1: Active Flow Monitoring—Multiple Port Mirroring with Next-Hop Groups Topology Diagram
Active Flow Monitoring—Multiple
Port Mirroring with Next-Hop Groups Topology Diagram

Figure 1 shows an example of how to configure multiple port mirroring with next-hop groups. All traffic enters the monitoring router at interface ge-1/0/0. A firewall filter counts and port-mirrors all incoming packets to a Tunnel Services PIC. A second filter is applied to the tunnel interface and splits the traffic into three categories: HTTP traffic, FTP traffic, and all other traffic. The three types of traffic are assigned to three separate next-hop groups. Each next-hop group contains a unique pair of exit interfaces that lead to different groups of packet analyzers and flow servers.

Note

Instances enabled to mirror packets to different destinations from the same PFE, also use different sampling parameters for each instance. When we configure Layer2 Port-mirroring with both global port-mirroring and instance based port-mirroring, PIC level instances will override FPC level and the FPC level will override the Global instance.

Example: Layer 2 Port Mirroring to Multiple Destinations

On MX Series routers, you can mirror traffic to multiple destinations by configuring next-hop groups in Layer 2 port-mirroring firewall filters applied to tunnel interfaces.

  1. Configure the chassis to support tunnel services at PIC 0 on FPC 2. This configuration includes two logical tunnel interfaces on FPC 2, PIC 0, port 10.

  2. Configure the physical and logical interfaces for three bridge domains and one Layer 2 VPN CCC:

    • Bridge domain bd will span logical interfaces ge-2/0/1.0 and ge-2/0/1.1.

    • Bridge domain bd_next_hop_group will span logical interfaces ge-2/2/9.0 and ge-2/0/2.0.

    • Bridge domain bd_port_mirror will use the logical tunnel interface lt-2/0/10.2.

    • Layer 2 VPN CCC if_switch will connect logical interfaces ge-2/0/1.2 and lt-2/0/10.1.

  3. Configure the three bridge domains and the Layer 2 VPN switching CCC:

    • Bridge domain bd spans logical interfaces ge-2/0/1.0 and ge-2/0/1.1.

    • Bridge domain bd_next_hop_group spans logical interfaces ge-2/2/9.0 and ge-2/0/2.0.

    • Bridge domain bd_port_mirror uses the logical tunnel interface lt-2/0/10.2.

    • Layer 2 VPN CCC if_switch connects interfaces ge-2/0/1.2 and lt-2/0/10.1.

    For detailed information about configuring the CCC connection for Layer 2 switching cross-connects, see the MPLS Applications User Guide.
  4. Configure forwarding options:

    • Configure global port-mirroring properties to mirror family vpls traffic to an interface on the bridge domain bd_port_mirror.

    • Configure the next-hop group nhg_mirror_to_bd to forward Layer 2 traffic to the bridge domain bd_next_hop_group.

    Both of these forwarding options will be referenced by the port-mirroring firewall filter:

  5. Configure two Layer 2 port-mirroring firewall filters for family bridge traffic:

    • filter_pm_bridge—Sends all family bridge traffic to the global port mirroring destination.

    • filter_redirect_to_nhg—Sends all family bridge traffic to the final next-hop group nhg_mirror_to_bd.

    Layer 2 port-mirroring firewall filters for family bridge traffic applies to traffic on a physical interface configured with encapsulation ethernet-bridge.

Release History Table
Release
Description
Starting with release 14.2, on routers containing an Internet Processor II application-specific integrated circuit (ASIC) or T Series Internet Processor, you can send a copy of an IP version 4 (IPv4) or IP version 6 (IPv6) packet from the router to an external host address or a packet analyzer for analysis.