In addition, ECMP ensures that all traffic forwarded to a given host address follows the same path, which is
selected from the possible next-hop routes.
For example, in the following figure, the ECMP inter-area routes to destination network 10.10.10.0/24 consist of
the following next-hop gateway addresses: 12.0.9.2, 13.0.9.3, and 14.0.9.4.
Figure 43: Example of OSPF ECMP multiple next-hop routing (inter-area)
However, the forwarding software distributes traffic across the three possible next-hop routes in such a way that
all traffic for a specific host is sent to the same next-hop router.
As shown in the following figure, one possible distribution of traffic to host devices is:
• Traffic to host 10.10.0.1 passes through next-hop router 12.0.9.2.
• Traffic to host 10.10.0.2 passes through next-hop router 13.0.9.3.
• Traffic to host 10.10.0.3 passes through next-hop router 12.0.9.2.
• Traffic to host 10.10.0.4 passes through next-hop router 14.0.9.4.
Figure 44: Example of traffic distribution on ECMP next-hop routers
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Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
Switch 16.08
