Resilient Hashing is a feature that ensures that there is minimal disruption in traffic flow when there is a disruption due to a link failure or a link addition. Resilient Hashing is supported for L3 traffic routed using BGP (support for both IPv4 and IPv6 traffic) and Static Routes. The resilient-hash is used to enable and disable this feature as well as configuring the maximum path value.
The default value for max-path is eight (8).
Global configuration and VRF configuration modes
Warning
Enabling or disabling Resilient Hashing or making changes to the max-path configuration value will cause traffic disruption for the corresponding VRF. This is by design. This is because, by design, routes and next-hops are re-downloaded to both the software and hardware routing tables for programming Special Attributes.
BFD sessions in unrelated VRFs are not affected. Additionally, when the device boots up, Resilient Hashing configuration replay will not cause BFD session flap.
Note
SLX 9540 and SLX 9640 support 64 maximum paths.The following example enables Resilient Hashing at a global level and sets the max-path value to 128. The show running-config resilient-hash command is used to verify the configuration.
SLX # conf term SLX (config)# SLX (config)# resilient-hash ecmp enable SLX (config)# resilient-hash max-path 128 SLX (config)# SLX (config)# do show running-config resilient-hash resilient-hash ecmp enable resilient-hash max-path 128 SLX (config)#
The following example enables Resilient Hashing at a VRF level and sets the max-path value to 64. The show running-config vrf <vrf-name> command is used to verify the configuration.
SLX # conf term SLX (config)# SLX (config)# vrf vrf2 SLX (config-vrf-vrf2)# SLX (config-vrf-vrf2)# resilient-hash ecmp enable SLX (config-vrf-vrf2)# resilient-hash max-path 64 SLX (config-vrf-vrf2)# do show running-config vrf vrf2 vrf vrf2 resilient-hash ecmp enable resilient-hash max-path 64 address-family ipv4 unicast ! address-family ipv6 unicast ! ! SLX (config-vrf-vrf2)#