Rules for measuring routing protocols

We know that this is a very important protocol for the selection of routing protocols. Because it manages the allocation of IP addresses in the browsing network, if this problem occurs, the entire network will not work properly. Now let's take a look at its measurement standards.

Measurement criteria

A router that knows multiple paths to a specific target network through the Routing Protocol) will select the path with the best measurement index and location in the routing table. If there are more than one Optimal measurement path, each path in these low-price paths will be placed in the routing table and the equivalent load balancing test will be conducted.

Different routing protocols use different standards. In other words, each of the various routing protocols has its own method to select the best path to the destination. This measure should be very advanced to ensure that the routing protocol can be used to explain the optimal path. The RIP protocol uses the Skip count as its metric. This is another restriction on this specific routing protocol. For example, if a vro has two paths leading to one destination, one path is a 56 K line, and the other path is a T-1 line, if the number of hops on the vro is the same, the RIP Protocol considers these two paths to be equivalent. Therefore, the RIP Protocol performs load balancing, although one path is 23 times faster than the other.

The OSPF protocol uses management costs as a measure. This standard can be set forcibly. In a Cisco router, this measurement standard is automatically calculated and is inversely proportional to the bandwidth of the link. The Nortel Network uses an alternative method to ensure OSPF equivalence by setting default values on all links.

VLSM

The importance of VLSM Variable Length subnet mask) has been described. The classless routing protocol supports VLSM because it carries a mask in route updates. Standard classless IP routing protocols include OSPF and RIP version 2. The first version of RIP is a type of classless routing protocol because it does not contain a subnet mask in route updates.

Route Aggregation

A routing protocol should support configurable route aggregation. The significance of setting route aggregation on the strategic point of the network has been introduced. In addition to configurable route aggregation, some protocols also have the automatic route aggregation function. This feature is not as good as it sounds, and sometimes it is an important cause of failure. The first version of RIP and other classless routing protocols automatically converge based on categories when the main network boundary broadcasts.

For example, if a vro is releasing a link announcement on a link in a specific B-type network, the subnet address 172.16.0.0 is sent to 172.16.0.0/16 as a single route. This requires a classifier routing protocol because it does not transmit the subnet mask. If the router does not have the interface of the main network, the downstream router cannot speculate on the subnet mask. Therefore, it must be assumed that it is generally an incorrect assumption) There is no subnet division.

If aggregation occurs at more than one point in the network, automatic route aggregation may cause a fault because the aggregation route may conflict. This situation occurs when a router receives the same aggregation route from the opposite two directions, and this situation is usually called a discontinuous network. You can think of a non-continuous network as "disconnected" by another network ". If the main network such as 172.16.0.0 is not continuous, the network in the middle is that the address is part of Class B 181.40.0.0) the router on will receive the 172.16.0.0/16 aggregation route from the opposite direction. These routers attempt to share the load in these routes. In actual cases, this may cause serious connection problems. TCP-based applications require resending every wrong route selection, and UDP-based applications cannot work at all!

Yes and no

The difference between the classless and classless routing protocols is very simple. The classless Protocol is included in the update subnet mask, and the classless Protocol does not include this subnet mask. However, the previous discussion should emphasize the fact that the consequences of such a simple difference are very important. The first version of RIP and other similar protocols do not support VLSM, discontinuous networks, or configurable route aggregation. Therefore, they are not applicable to modern networks.

Scalability

Scalability problems are related to the ability of the routing protocol to support network upgrades. That is, when more IP subnets are added to the network, the routing protocol can fully support the operation of the upgraded network. Convergence speed, support for VLSM, and configurable route aggregation will ultimately determine the scalability of this routing protocol. The efficiency of routing protocol switching is also related to scalability. RIP and other distance vector protocols regularly broadcast the entire route table to adjacent routers. Once the original route information changes, more advanced protocols only broadcast event-driven network topology changes, which is obviously a more efficient mechanism.