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EX Series MC-LAG Fabric Upgrade Procedure

 

About This Network Configuration Example

This network configuration example (NCE) shows how to manually upgrade an MC-LAG pair of EX series devices. This process minimizes service disruption and has minimal impact on data center workloads.

Use Case Overview

To eliminate the access switch as a single point of failure in a data center environment, multichassis link aggregation groups (MC-LAGs) enable a client device to form a logical LAG interface between two MC-LAG peers. An MC-LAG provides redundancy and load balancing between the two MC-LAG peers, multihoming support, and a loop-free Layer 2 network without running STP. This example uses a basic MC-LAG configuration, but you can use this process for many different use cases.

This example does not cover how to perform a non-stop software upgrade (NSSU).

Technical Overview

Manually upgrading MC-LAG peers is similar to an NSSU. The manual upgrade process uses a high-availability design to systematically remove one device from service in order to perform the upgrade and then reboot. When servers are dual-homed to each MC-LAG peer, the network can handle the removal of one of the MC-LAG peers during the upgrade window. There’s a reduction of overall network bandwidth during the process, but the network remains available.

The MC-LAG is in active-active state and uses the ICCP protocol to keep the device state synchronized between the members of the MC-LAG. While one peer handles the traffic, the other peer is taken offline to upgrade the software.

Figure 1 illustrates a basic MC-LAG topology.

Figure 1: Basic MC-LAG Topology
Basic MC-LAG Topology

Here’s the sequence of events that occur during an upgrade between two MC-LAG peers (Node 1 and Node 2):

  1. All traffic is shifted from Node 1 to Node 2.

  2. Node 1 is no longer handling traffic, so the MC-LAG is no longer operational.

  3. Software is installed on Node 1 and then reboots.

  4. Node 1 comes online, and all traffic is shifted from Node 2 to Node 1.

  5. Software is installed on Node 2 and then reboots.

  6. When Node 2 is online, the MC-LAG interfaces are re-enabled between the Node 1 and Node 2.

How to Perform an EX Series MC-LAG Fabric Upgrade

Requirements

This example uses the following hardware and software components:

  • Two EX9251 devices running Junos OS Release 18.2R3

  • Junos OS Release 18.4R2

  • A test server running Ubuntu Linux 16.04

Overview

To ensure a minimum of downtime, upgrading between software releases requires a sequence of steps coordinated among all of the network elements This topology uses servers with redundant connections to the MC-LAG to achieve high-availability during the switch over between MC-LAG peers.

To upgrade the fabric to a new version of Junos OS with minimal traffic disruption, you need to disable the MC-LAG and upgrade the MC-LAG peers as standalone units. After the software has been upgraded on both MC-LAG peers, you will re-connect them and re-establish the MC-LAG.

Topology

Figure 2 illustrates the MC-LAG topology referred to in this example.

Figure 2: Topology
Topology

EX Series MC-LAG Fabric Upgrade Configuration

Step-by-Step Procedure

Use this procedure to upgrade both peers of a MC-LAG fabric consisting of EX9200 switches to the same Junos OS Release version. We strongly recommend that both members of the MC-LAG are the same platform.

This configuration example shows how to manually upgrade MC-LAG peers from Junos OS Release 18.2R3-S3 to Junos OS Release 18.4R3.3.

  1. Verify that the MC-LAG state is operational between both MC-LAG peers by checking the MC-LAG parameters.

Upgrade the EX Series MC-LAG Fabric

Step-by-Step Procedure

  1. Copy the new Junos OS software image to the /var/tmp directories on both peers.

    Copying the software on both MC-LAG peers stages the software for the upgrade procedure. The copy operation takes some time to complete while it transfers the Junos OS software images from the server to the MC-LAG peers.

  2. Disable the server-facing interfaces on EX9251-A to minimize disruption during the switch over to EX9251-B.
    Figure 3: Disabling the Server-Facing Interface on EX9251-A
    Disabling the Server-Facing
Interface on EX9251-A
  3. Disable the uplink interfaces on EX9251-A.
  4. Disable the interfaces between the EX9251-A and EX9251-B.

    This breaks up the MC-LAG.

    Figure 5: Disabling Interfaces Between EX9251-A and EX9251-B
    Disabling Interfaces Between
EX9251-A and EX9251-B
  5. Upgrade EX9251-A.
    Figure 6: Upgrading EX9251-A
    Upgrading EX9251-A
  6. To redirect the traffic from EX9251-B to EX9251-A, re-enable the server-facing and uplink interfaces on EX9251-A.
    Figure 7: Re-enabling Server-Facing and Uplink Interfaces
    Re-enabling Server-Facing and Uplink
Interfaces
  7. Disable the server-facing interfaces on EX9251-B.
    Figure 8: Disabling Server-Facing Interfaces on EX9251-B
    Disabling Server-Facing
Interfaces on EX9251-B
  8. Disable the uplink interfaces on EX9251-B, so that the traffic goes through EX9251-A.
    Figure 9: Disabling Uplink Interfaces on EX9251-B
    Disabling Uplink Interfaces
on EX9251-B
  9. Upgrade EX9251-B.
    Figure 10: Upgrading EX9251-B
    Upgrading EX9251-B
  10. Re-enable the ICCP-PL interface between EX9251-A and EX9251-B.
  11. Re-enable the server-facing and uplink interfaces on EX9251-B.

Verification

Verify that the MC-LAG Fabric is Operational

Purpose

Verify that the MC-LAG Fabric is operational.

Action

Meaning

You can see that the MC-LAG is operational because the MC-AE interface and ICCP connections are up.

Verify that the New Version of Junos OS is Installed

Purpose

Verify that the new version of Junos OS is installed on EX9251-A and EX9251-B.

Action

Meaning

You can see that Junos OS 18.4R2.7 is installed on EX9251-A and EX9251-B.

Conclusion

Now you can manually upgrade an EX Series MC-LAG Fabric with minimal impact to your data center workloads. You can use this procedure to upgrade any MC-LAG configuration with a similar topology.

Device Configuration Details

Step-by-Step Procedure

This is the MC-LAG configuration used in this example.

EX9251-A

Step-by-Step Procedure

EX9251-B