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In static routing or dynamic routing, an example is clear! Jun of the document is going to travel all the way from Beijing to Sanya, and uses examples of "group tour" and "individual trip" to show you "static route" and "dynamic route".

The book follows the above, and the document has thought twice about choosing the "individual travel" mode of travel, so which route generated by the dynamic routing protocol should be chosen?

Do you choose the "sightseeing tour" recommended by dynamic routing protocol 1?

Or "hiking" recommended by dynamic routing protocol 2?

Is it a taste of culture? Or explore food all the way?

There are ten million roads, which one should be chosen?

We have to mention "routing mode of dynamic routing protocol" and "routing priority" ~

1. How is the dynamic routing protocol routed? Multiple dynamic routing protocols can be run on a router at the same time, different dynamic routing protocols have their own standards to measure the quality of the route, and each dynamic routing protocol sends what it thinks is the best route to the router.

In this way, to the same destination address, there may be multiple different routes selected by different dynamic routing protocols.

For example, routes generated by "dynamic routing protocols" are like "recommended routes" intelligently generated in "travel software". Each "recommended route" is measured in terms of physical strength, cost, food, and so on.

The same is true of different dynamic routing protocols, which are measured according to performance parameters such as path length, reliability, delay, bandwidth, load and so on.

However, because the measurement methods of different protocols are slightly different, just as the recommendation algorithms of different travel routes are slightly different, then the meaning of the measure is also different, so it is only referential, but does not have accurate comparability.

In any case, the router must choose the "best route" calculated by one of the routing protocols as the forwarding path and add it to the routing table.

At this point, we need "routing priority" ~

2. What is the routing priority? When choosing a route for a trip, you can mark "routing priority" for many recommended routes according to your travel preferences, and then choose the recommended route with the highest "routing priority", and you can set out the most desirable route for PICK!

In practical application, routing priority is also known as "routing administrative distance", which is used to distinguish the priority of dynamic routing protocols.

We assign different routing priorities to different routing protocols (including static routes), and a low value indicates a high routing priority.

When there are multiple routes to the same destination address, one of the lowest priority values can be selected as the optimal route according to the route priority value, and the route can be written into the routing table at the same time.

So what is the priority of common routing protocols?

See the following table:

Route type Route priority directly connected Route (Direct) 0 static Route (Static) 1OSPF110RIP120IBGP200Special (used for internal processing) 255Tips

Directly connected routes: directly connected routes can only obtain routing information directly connected to the router, and those that are not directly connected are powerless.

Non-directly connected routes: routes learned from other routers through routing protocols are called non-directly connected routes and are divided into static routes and dynamic routes.

With the exception of directly connected routes, the priority values of various routing protocols can be manually adjusted by the administrator.

The default route priority is assigned as follows:

Directly connected routes have the highest priority.

Manually set route entries take precedence over dynamically selected route entries.

Routing protocols with complex metric algorithms have higher priority than routing protocols with simple metric algorithms.

3. QA OSPF routing protocol and RIP routing protocol each recommend a route, so which protocol will the router choose first?

A.RIP

B.OSPF

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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