Equal cost routing (ECMP) means that there are multiple different routing paths with equal cost values to reach the same destination IP or destination network segment.
#When the device supports equal-cost routing, the Layer 3 forwarding traffic sent to the destination IP or destination network segment can be shared through different paths to achieve network load balancing, and when some of the paths fail, other paths will take over to complete the forwarding processing to achieve the routing redundancy backup function. (Recommended learning: web front-end video tutorial)
The principle is that there are two or more routes to the same destination address with the same cost and different next hops. Expand all Equal Cost Routing (ECMP) That is, there are multiple different routing paths with equal Cost values to reach the same destination IP or destination network segment.
ECMP (Equal-CostMultipathRouting) equal-cost multipath, in a network environment where there are multiple different links to the same destination address, if traditional routing technology is used, data packets sent to the destination address can only use For one of the links, the other links are in backup or invalid state, and it takes a certain amount of time to switch between each other in a dynamic routing environment. However, the equal-value multipath routing protocol can use multiple links at the same time in this network environment, not only The transmission bandwidth is increased, and data transmission of failed links can be backed up without delay or packet loss.
The biggest feature of ECMP is that it achieves the purpose of multi-path load balancing and link backup under equal value conditions. ECMP functions are basically supported in static routing and OSPF.
But the actual situation is that the bandwidth, delay and reliability of each path are different. If the Cost is recognized as the same, the bandwidth cannot be used well. Especially when the difference between paths is large, the effect will be very different. ideal.
For example, if the router has two exits and two paths, one has a bandwidth of 100M and the other has a bandwidth of 2M. If ECMP is deployed, the total network bandwidth can only achieve a utilization rate of 4M.
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