Introduction to the basic concepts of the VPN Protocol

In the routing protocol, the OSPF protocol is a special protocol. Let's introduce this agreement today. So everyone should be clear. The VPN Protocol is Cisco's private Routing Protocol, which combines the advantages of Distance Vector and link state 2. It is "Enhanced Interior Gateway Routing Protocol ", the VPN Protocol has the following features:

1. Reduce bandwidth usage: no periodic update is made for the network. It is only updated after the route path and degree change.

2. Support for multiple network layer protocols: by using the "protocol-related modules", VPN gateway can support IPX, ApplleTalk, IP, IPv6, NovellNetware, and other protocols.

3 .. fast Convergence: the Link-State Packet (LSP) forwarding does not rely on route computing, so large networks can quickly converge. it only declares the link and link status, rather than the route, so even if the link changes, it will not cause the route of the link to be declared. however, the link status routing protocol uses the Dijkstra algorithm, which is more complex and occupies more CPU and memory resources than other routing protocols that calculate routes separately, the link status routing protocol uses diffusingcomputations. Multiple routers use parallel memory routing computing to quickly converge without loops.

4. seamlessly connect to the data link layer protocol and Topology: routing information can be seamlessly exchanged between the OSPF protocol and IGRP with the same autonomous system number ｡

The OSPF communication must establish a neighbor, while the neighbor building concern must meet the following conditions:

1. Receive HELLO message or ACK

2. Match the AS number

3. Must have the same measurement

Note: The network type of the network in the source image is the same as that in the source image.

The following table lists the routing and maintenance information of the OSPF protocol:

1. Neighbor table: created Neighbor Relationship

2. Topology table: Route notifications received by each Router from each neighbor on the Internet

3. Route table: the current route used for route determination has a measurement, such as bandwidth, latency, load, reliability, and maximum transmission unit ｡

VPN is the default METRIC parameter. The management distance is used to select the routing protocol, and the Management Distance is 90.