- Network > Virtual Routers > Router Settings > ECMP
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 a packet.
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 and, for Router Settings, select the ECMP tab and configure the ECMP Settings as described.
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