Fast Reroute Protection - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

JUNOSe 11.0.x IP, IPv6, and IGP Configuration Guide
The random algorithm does not guarantee equal distribution of the packets among
the ECMP links.
ip multipath round-robin
maximum-paths

Fast Reroute Protection

If a link goes down, ECMP uses fast reroute protection to shift packet forwarding to
use operational links, thereby decreasing packet loss. Fast reroute protection updates
ECMP sets for the interface without having to wait for the route table update process.
When the next route table update occurs, a new ECMP set can be added with fewer
links or the route might point to a single next hop.
CAUTION: To provide ECMP fast reroute functionality in the event of an interface
failure, the members of an equal cost multipath must be resolved to corresponding
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IP Routing
Use to specify round-robin as the mode for ECMP load sharing on an interface.
ECMP uses the round-robin mode when you have configured all interfaces in the
set to round-robin. Otherwise, ECMP defaults to hashed mode because
round-robin mode can cause reordering of packets. You must explicitly ensure
that the possible reordering is acceptable on all the member interfaces by setting
them to round-robin mode.
If one of the ECMP next hops is an indirect next hop, ECMP uses hashed mode
load balancing.
Example
host1(config)#virtual-router router_0
host1:router_0(config)#interface serial 4/0:1/22.22
host1:router_0(config-subif)#ip multipath round-robin
host1:router_0(config-subif)#exit
Use the no version to set the ECMP mode to the default, hashed.
See ip multipath round-robin
Use to control the maximum number of parallel routes that the routing protocol
supports.
The maximum number of routes can be in the range 1–16 for BGP, IS-IS, OSPF,
or RIP.
Example
host1(config-router)#maximum-paths 2
Use the no version to restore the default value, 1 for BGP or 4 for IS-IS, OSPF,
or RIP.
See maximum-paths