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 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.
Make use of the available bandwidth on all 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 waiting for the routing protocol
or RIB table to elect an alternative path, which can help reduce
down time when links fail.
ECMP load balancing is done at the session level, not at the
packet level. This means the firewall chooses an equal-cost path
at the start of a new session, not each time the firewall receives
Enabling, disabling, or changing ECMP on an existing virtual
router causes the system to restart the virtual router, which might cause
existing sessions to be terminated.
To configure ECMP for a virtual router, select a virtual router