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

The graceful Routing Engine switchover (GRES) feature in Junos OS enables QFX10000 switches 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, a QFX10000 switch could experience Layer 3 traffic loss if traffic is flowing during the switchover or reboot of the Routing Engine.

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.


The recommended hold-time value in an EVPN/VXLAN environment is 300 seconds (5 minutes).

  • Enable GRES

  • Enable NSR

To specify a hold-time interval that prevents phantom routes from being added to the routing table during a switchover until the interval expires:

Specify a hold-time interval of 300.

The hold-time interval range is 0 through 10000.