ECMP route failover and load balancing Router Static
FortiGate Version 4.0 MR1 Administration Guide
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Figure 180: Edit Static Route
ECMP route failover and load balancing
FortiOS uses equal-cost multi-path (ECMP) to distribute traffic to the same destination
such as the Internet or another network. Using ECMP you can add multiple routes to the
destination and give each of those routes the same distance and priority.
Using ECMP, if more than one ECMP route is available you can configure how the
FortiGate unit selects the route to be used for a communication session. If only one ECMP
route is available (for example, because an interface cannot process traffic because
interface status detection does not receive a reply from the configured server) then all
traffic uses this route.
Previous versions of FortiOS provided source IP-based load balancing for ECMP routes.
FortiOS 4.0 MR1 includes three configuration options for ECMP route failover and load
balancing:
Destination
IP/Mask
Type the destination IP address and network mask of packets that the
FortiGate unit has to intercept. The value 0.0.0.0/0.0.0.0 is reserved
for the default route.
Gateway Type the IP address of the next-hop router to which the FortiGate unit will forward
intercepted packets.
Device Select the name of the FortiGate interface through which the intercepted packets
may be routed to the next-hop router.
Distance Type an administrative distance from 1 to 255 for the route. The distance value is
arbitrary and should reflect the distance to the next-hop router. A lower value
indicates a more preferred route.
Weight If ECMP Route Failover & Load Balance Method is set to weighted add weights for
each route. Add higher weights to routes that you want to load balance more
sessions to. See “Configuring weighted static route load balancing” on page 348.
Note: If multiple routes to the same destination have the same priority but different
distances, the route with the lowest distance is used. If multiple routes to the same
destination have the same distance but different priorities, the route with the lowest priority
is used. Distance takes precedence over priority. If multiple routes to the same destination
have the different distances and different priorities, the route with the lowest distance is
always used even if it has the highest priority.
Source based
(also called
source IP based)
The FortiGate unit load balances sessions among ECMP routes based on the
source IP address of the sessions to be load balanced. This is the default load
balancing method. No configuration changes are required to support source IP
load balancing.