Example: Configuring Aggregated Ethernet Load Balancing

 

This example shows how to configure aggregated Ethernet load balancing.

Requirements

This example uses the following hardware and software components:

  • Three MX Series routers with MIC and MPC interfaces or three PTX Series Packet Transport Routers with PIC and FPC interfaces

  • Junos OS Release 13.3 or later running on all devices

Overview

Load balancing is required on the forwarding plane when there are multiple paths or interfaces available to the next hop router, and it is best if the incoming traffic is load balanced across all available paths for better link utilization.

Aggregated Ethernet bundle is a typical application that uses load balancing to balance traffic flows across the member links of the bundle (IEEE 802.3ad).

Starting with Junos OS Release 13.3, aggregated Ethernet load balancing is enhanced to provide two solutions for resolving genuine traffic imbalance on aggregated Ethernet bundles on MICs or MPCs of MX Series routers. Starting with Junos OS Release 14.1, aggregated Ethernet load balancing is enhanced to provide two solutions for resolving genuine traffic imbalance on aggregated Ethernet bundles on PICs or FPCs of PTX Series Packet Transport Routers.

The aggregated Ethernet load-balancing solutions are:

  • Adaptive—Adaptive load balancing is used in scenarios where flow-based hashing is not sufficient to achieve a uniform load distribution. This load-balancing solution implements a real-time feedback and control mechanism to monitor and manage imbalances in network load.

    The adaptive load-balancing solution corrects the traffic flow imbalance by modifying the selector entries, and periodically scanning the link utilization on each member link of the AE bundle to detect any deviations. When a deviation is detected, an adjustment event is triggered and fewer flows are mapped to the affected member link. As a result, the offered bandwidth of that member link goes down. This causes a continuous feedback loop, which over a period of time ensures that the same amount of byte rate is offered to all the member links, thus providing efficient traffic distribution across each member link in the AE bundle.

    To configure adaptive load balancing, include the adaptive statement at the [edit interfaces aex aggregated-ether-options load-balance] hierarchy level.

    Note

    Adaptive load balancing is not supported if the VLAN ID is configured on the aggregated Ethernet interface. This limitation affects the PTX Series Packet Transport Routers only.

    The pps option enables load balancing based on the packets-per-second rate. The default setting is bits-per-second load balancing.

    The scan-interval value configures the length of time for scanning as a multiple of 30 seconds.

    The tolerance value is the limit to the variance in the packet traffic flow to the aggregated Ethernet links in the bundle. You can specify a maximum of 100-percent variance. When the tolerance attribute is not configured, a default value of 20 percent is enabled for adaptive load balancing. A smaller tolerance value balances better bandwidth, but takes a longer convergence time.

    Note

    The pps and scan-interval optional keywords are supported on PTX Series Packet Transport Routers only.

  • Per-packet random spray—When the adaptive load-balancing solution fails, per-packet random spray acts as a last resort. The per-packet random spray load-balancing solution helps to address traffic imbalance by randomly spraying the packets to the aggregate next hops. This ensures that all the member links of the AE bundle are equally loaded, resulting in packet reordering.

    In addition, per-packet random spray identifies the ingress Packet Forwarding Engine that caused the traffic imbalance and eliminates traffic imbalance that occurs as a result of software errors, except for packet hash.

    To configure per-packet random spray load balancing, include the per-packet statement at the [edit interfaces aex aggregated-ether-options load-balance] hierarchy level.

    Note

    The Per-Packet option for load balancing is not supported on the PTX Series Packet Transport Routers.

The aggregated Ethernet load-balancing solutions are mutually exclusive. When more than one of the load-balancing solutions is configured, the solution that is configured last overrides the previously configured one. You can verify the load-balancing solution being implemented by issuing the show interfaces aex aggregated-ether-options load-balance command.

Topology

In this topology, two aggregated Ethernet bundles - ae0 and ae1 - are configured on the links between the R2 and R3 routers.

Figure 1: Aggregated Ethernet Load Balancing
 Aggregated Ethernet Load Balancing

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

R1

R2

R3

Configuring Adaptive Load Balancing

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure the R2 router:

Note

Repeat this procedure for the other routers, after modifying the appropriate interface names, addresses, and any other parameters for each router.

  1. Specify the number of aggregated Ethernet interfaces to be created.
  2. Configure the Gigabit Ethernet interface link connecting R2 to R1.
  3. Configure the five member links of the ae0 aggregated Ethernet bundle.
  4. Configure the eight member links of the ae1 aggregated Ethernet bundle.
  5. Enable aggregate Ethernet load balancing on ae0 of R2.
  6. Configure the link speed for the ae0 aggregated Ethernet bundle.
  7. Configure LACP on the ae0 aggregated Ethernet bundle.
  8. Configure the interface parameters for the ae0 aggregated Ethernet bundle.
  9. Enable aggregate Ethernet load balancing on ae1 of R2.
  10. Configure the link speed for the ae1 aggregated Ethernet bundle.
  11. Configure LACP on the ae1 aggregated Ethernet bundle.
  12. Configure the interface parameters for the ae1 aggregated Ethernet bundle.
  13. Disable selective aggregate Ethernet statistics.
  14. Configure RSVP on all the interfaces of R2 and on the AE bundles.
  15. Configure MPLS on all the interfaces of R2 and on the AE bundles.
  16. Configure IS-IS on all the interfaces of R2 and on the AE bundles.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show accounting-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

Confirm that the configuration is working properly.

Verifying Adaptive Load Balancing on ae0

Purpose

Verify that packets received on the ae0 aggregated Ethernet bundle are load-balanced among the five member links.

Action

From operational mode, run the show interfaces ae0 extensive command.

user@R2> show interfaces ae0 extensive

Meaning

The member links of the ae0 aggregated Ethernet bundle are fully utilized with adaptive load balancing.

Release History Table
Release
Description
Starting with Junos OS Release 14.1, aggregated Ethernet load balancing is enhanced to provide two solutions for resolving genuine traffic imbalance on aggregated Ethernet bundles on PICs or FPCs of PTX Series Packet Transport Routers.
Starting with Junos OS Release 13.3, aggregated Ethernet load balancing is enhanced to provide two solutions for resolving genuine traffic imbalance on aggregated Ethernet bundles on MICs or MPCs of MX Series routers.