Complexity of BGP control route Flow

The BGP protocol is designed for routing between autonomous systems, but it can also be used inside autonomous systems and is a type of Dual Routing Protocol.

Two BGP adjacent nodes that can communicate between autonomous systems must exist on the same physical link.

BGP routers in the same autonomous system can communicate with each other to ensure that they share the same information for the entire autonomous system. After information exchange, they will determine which BGP router in the autonomous system is used as the connection point to receive information from outside the autonomous system.

1. The BGP protocol is a strategic Routing Protocol. Its complexity is not due to the difficulty of routing algorithms. The most important thing is to use BGP to control the routing flow in a diversified manner, any routing protocol must first solve the loop problem. OSPFISIS uses the SPF algorithm to solve the problem. The OSPF algorithm is novel and a Diffusion algorithm, therefore, BGP uses a lot of small means in the design to focus on designing diverse control attributes.

Ii. BGP is an important attribute inherent in BGP. In ASPATH and BGP Route update, the passed self-developed domain (AS) number is added to the update. In this way, when BGP finds that its own AS is also in it, it can be considered that a loop has occurred. EBGP can consider this AS no problem. In some scenarios, there will be problems, whether it is manual or BGP's automatic summary attribute, It is summarized into 10.233.40.0/17 and uploaded to AS300, and then transmitted back to AS100. In AS100's view, the ASPATH of this route is (300,200) and is not in it !! This will lead to the formation of the loop.

3. The solution is to increase the ASSET value so that the original aspath attribute value is retained after route aggregation (aggregation), so that the routing loop can be prevented, this flag method can be used to transfer between AS without loops. The problem arises. What if it is in an?

In IBGP, the conversion from the beginning to the end is performed in an AS, and ASPATH is not necessary. Therefore, IBGP does not add the ASPATH attribute in BGP. How can this problem be solved?

4. developers think of a wonderful idea. If IBGP is passed in the adjacent areas, it means one-to-one. For example, I know A and A know B, but I don't know B, because A won't introduce me to each other.

If such a rule is stipulated in BGP, Routes learned by IBGP are not published to other IBGP joining groups, so they cannot prevent loops, because they cannot generate loops and are all a line.

5. At this time, we can consider this issue based on the OSPF logic. If we find a representative, we will not solve it, that is, DR + BDR. in order to indicate that hi-tech has a pull-up name: Route reflectors, that is, RR. In this way, you can logically change to a simple hub-spoke structure. In fact, this idea is to partially release the hidden rules described above in section 3rd. That is, a man-in-the-middle mechanism is created to enable the man-in-the-middle mechanism to introduce the customers it knows to other customers.

In order to prevent loops, some fairness rules must be implemented for middlemen. Most importantly, middlemen cannot change the information sent by customers.

Even if the loop information is passed back, you can find your own RID from the update. That's why LOOPBACK is configured. How important is that, in MPLS, the request must be/32 bits, and the loop can be discovered. By dividing an AS into several small as s, the small AS s are adjacent with EBGP, use RR in small.