Equal Cost Multiple Path (ECMP) processing is a networking
feature that enables the firewall to use up to four equal-cost routes
to the same destination. Without this feature, if there are multiple
equal-cost routes to the same destination, the virtual router chooses
one of those routes from the routing table and adds it to its forwarding
table; it will not use any of the other routes unless there is an
outage in the chosen route.
Enabling ECMP functionality on a virtual router allows the firewall
to have up to four equal-cost paths to a destination in its forwarding
table, allowing the firewall to:
Load balance flows (sessions) to the same destination
over multiple equal-cost links.
Efficiently use all available bandwidth on links to the same
destination rather than leave some links unused.
Dynamically shift traffic to another ECMP member to the same
destination if a link fails, rather than having to wait for the
routing protocol or RIB table to elect an alternative path/route.
This can help reduce downtime when links fail.