Vro policy and vro Policy

Source: Internet
Author: User

I have always been confused about the differences between routing policies and policy routes. based on my own experience and some references, I have summarized the differences between routing policies and policy routes!

I. Routing Policy

A routing policy is a route publishing and receiving policy. In fact, selecting a routing protocol is also a routing policy, because the same network structure, different routing protocols may generate different route tables because of different implementation mechanisms, different overhead calculation rules, and different priority definitions. These are the most basic.

Generally, what we call a routing policy is that, based on the normal routing protocol, we change the result of Route generation, release, and selection based on a rule, by changing certain parameters, or by setting a certain control mode. Note that the result (that is, the route table) is changed ), the rules are not changed, but are applied.

Ii. Policy Routing

When a route table has been generated, a policy route is not forwarded according to the existing route table. Instead, a policy route is selected based on certain communication traffic.

Iii. Connection and Difference


Both parties select the path for packet forwarding, and change certain parameters or control methods according to certain rules to set different forwarding paths.


A routing policy uses a policy to change the routing discovery result based on the rules that affect the route Publishing, receiving, or routing parameters. The route table content is eventually changed. It is used in route discovery.

Although there are currently the optimal routes, policy routes use different forwarding paths separately for some special hosts (or applications or protocols) that do not use the forwarding paths in the current route table. When the data packet is forwarded, it does not change any content in the routing table.

The priority of a policy route is higher than that of a route policy. When the router receives and forwards data packets, it first matches the rule of the policy route, the forwarding is based on the route policy. Otherwise, the forwarding is based on the forwarding path in the route table.

To sum up, the routing policy is a routing discovery rule, and the policy route is a packet forwarding rule. In fact, "Policy Routing" is understood as "forwarding policy", which makes it easier to understand and distinguish. Because the forwarding is at the bottom layer and the routing is at the top layer, the forwarding priority is higher than the routing priority, which is understandable.

In fact, there are two types and layers of tables in the vro, one is the routing-table, and the other is the forwarding table ). The forwarding table is mapped from the route table. A policy route directly acts on the forwarding table, and a routing policy acts on the route table.

Iv. Advantages and Disadvantages

The network communication rule is to have a route before forwarding. The routing policy only works when a route is detected. After the route table is generated and stable, if the network does not change, the route table usually does not change. At this time, without an application, the routing policy does not occupy resources.

Policy Routing acts upon forwarding. After a router initially generates a route table, the basic workload is on packet forwarding. If there is no policy routing, the router only needs to analyze the destination address of each data packet, match the route table to determine the next hop;

However, if there is a policy route, the policy route is always in the application state. If the policy route is particularly complex, the router should judge the source address, protocol, or application of the data packet based on the Rule, this will occupy a large amount of resources, so unless you have to, try to use routing policies instead of using policy routing.

This should be taken into consideration during network optimization. If the policy routing is particularly complex, you can simply break down the network to eliminate the Policy Routing as much as possible. Otherwise, the router will be heavily burdened.

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