PIM NSR and Unified ISSU Support for VXLAN Overview

The Layer 2 address learning daemon (l2ald) passes VXLAN parameters (VXLAN multicast group addresses and the source interface for a VXLAN tunnel [vtep-source-interface]) to the routing protocol process on the primary Routing Engine. The routing protocol process forms PIM joins with the multicast routes through the pseudo-VXLAN interface based on these configuration details.

Because the l2ald daemon does not run on the backup Routing Engine, the configured parameters are not available to the routing protocol process in the backup Routing Engine when NSR is enabled. The PIM NSR mirroring mechanism provides the VXLAN configuration details to the backup Routing Engine, which enables creation of the required states. The routing protocol process matches the multicast routes on the backup Routing Engine with PIM states, which maintains the multicast routes in the Forwarding state.

In response to Routing Engine switchover, the multicast routes remain in the Forwarding state on the new primary Routing Engine. This prevents traffic loss during Routing Engine switchover. When the l2ald process becomes active, it refreshes VXLAN configuration parameters to PIM.

This feature does not introduce any new CLI commands. You can issue the following show commands on the backup Routing Engine to monitor the PIM joins and multicast routes on the backup Routing Engine:

• show pim join extensive

• show multicast route extensive

Unified ISSU Support

Starting in Junos OS Release 17.2 R1, unified in-service software upgrade is supported for VXLAN using PIM on MX Series routers. ISSU enables you to upgrade your Junos OS software on your MX Series router with no disruption on the control plane and with minimal disruption of traffic. Unified ISSU is supported only on dual Routing Engine platforms. The graceful Routing Engine switchover (GRES) and nonstop active routing (NSR) features must both be enabled. Unified ISSU allows you to eliminate network downtime, reduce operating costs, and deliver higher levels of services. See Getting Started with Unified In-Service Software Upgrade.

To enable GRES, include the graceful-switchover statement at the  [edit chassis redundancy] hierarchy level.

To enable NSR, include the nonstop-routing statement at the [edit routing-options] hierarchy level and the commit synchronize statement at the [edit system] hierarchy level.