Dynamic routing protocols are divided into Internal Gateway Protocol (IGP) and External Gateway Protocol (EGP), depending on whether they are used within an autonomous domain. The autonomous domain here refers to a network with a unified management authority and a unified routing policy. The routing protocol adopted within the autonomous domain is called the Internal Gateway Protocol, which is commonly used in RIPandOSPF, and theexternal Gateway protocol is mainly applied to routing between multiple autonomous domains, which is commonly used BGP and BGP-4.
1.RIPProtocol
Rip ( routing information protocol ) routing Information Protocol: is in a rip There are two versions: Span style= "font-family: ' Times New Roman ';" >ripv1 and ripv2 15 jump.  
the algorithm of RIP is simple, but the convergence speed is slow when the path is high, the bandwidth resource occupied by broadcast routing information is more, it is suitable for the small network with relatively simple network topology and low failure rate of data link, in large-scale network, RIP is not used generally .
RIP uses UDP packets to update routing information. The router Updates the routing information every 30s, and if there is no response from the neighboring router within 180s , it is considered that the route to the router is not available and the router is unreachable. If the router's answer is still not received after 240s, the routing information about the router is removed from the routing table.
RIP has the following characteristics:
Routers of different vendors can be connected by RIP ;
Simple configuration;
Suitable for small networks (less than hop);
RIPV1 does not support VLSM;
Need to consume WAN bandwidth ;
Consumes CPUand memory resources.
2.OSPFProtocol
OSPF( open shortestpathfirst) protocol: Using link state routing technology, Open Shortest Path first algorithm. Routers send each other directly connected link information and the link information it has to other routers. Each OSPF Router maintains a database of the same autonomous system topology. From this database, the shortest path tree is constructed to calculate the way out of the table. When the topology changes, OSPF can quickly recalculate the path, generating only a small amount of routing protocol traffic.
Key Benefits:
Fast convergence speed, no jump limit;
Support Service type routing
Provides load balancing and identity authentication
Applicable environment
Large-scale, environment-complex Internet
3.BGPProtocol
BGP (Border Gateway Protocol,Border Gateway Protocol ) is a routing protocol between autonomous systems. BGP is used to connect to the Internet. As the latest external gateway protocol, there are four versions available.
BGP is the only network protocol that handles the size of the Internet, and is the only one that can properly handle a multi-link protocol between well-connected routing domains. BGPv4 is an external routing protocol. It can be considered as an advanced distance vector routing protocol.
BGP Features:
BGP is an external routing protocol that differs from OSPFandRIP in that it does not focus on discovering and computing routes, but on controlling the propagation of routes and choosing the best routes.
BGP can completely solve the routing loop problem by carrying the as path information.
In order to control the propagation of routes and the selection of routes, attribute information is included for routing.
TCP is used as its transport layer protocol, which improves the reliability of the protocol. Port number 179.
BGP-4 supports CIDR(Classless Inter-domain routing), andthe introduction ofCIDR simplifies route aggregation and reduces routing tables.
BGP updates only send incremental routes, reducing The bandwidth consumed by BGP propagation routes.
Provides a rich routing strategy.
Routing protocol RIP, OSPF, BGP comparison