Preventing Traffic Loss in an EVPN-VXLAN Environment With GRES and NSR

The graceful Routing Engine switchover (GRES) feature in Junos OS enables devices with redundant Routing Engines to continue forwarding packets, even if one Routing Engine fails. To preserve routing during a switchover, GRES is combined with nonstop active routing (NSR).

Although GRES preserves interface and kernel information, in an EVPN-VXLAN environment, switches in the QFX10000 line might experience Layer 3 traffic loss if traffic is flowing during the switchover or during the Routing Engine reboot operation.

Note:

This section doesn't apply to QFX10002 switches because those devices don't have redundant Routing Engines and don't support GRES.

To prevent traffic flows from being dropped in such a scenario, configure a hold-time interval that prevents IP phantom addresses from being added to the routing tables. During this interval, the routes are maintained in the kernel. After the interval expires, the phantom routes are added to the appropriate routing tables before they are deleted from the kernel.

Note:

We recommended a hold-time value of 300 seconds (5 minutes) in EVPN-VXLAN environments.