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Basic concepts of .VRRP

VRRP (Virtual routing redundancy Protocol): by combining several routing devices to form a virtual routing device, the ip address of the virtual routing device is used as the default gateway address of the user to communicate with the outside world. When the gateway equipment fails, the VRRP protocol can quickly select new gateway equipment to bear the data traffic and ensure the reliable communication of the network. VRRP uses the ip message as the transmission protocol message, the protocol number is 112.It is sent with a fixed multicast address 224.0.0.18. The gateway backup function is realized by selecting a router as the master and other devices as the backup. Only advertisement messages are used by VRRP.

Border Gateway Protocol (BGP) is a routing protocol of an autonomous system running on TCP. BGP is the only protocol used to handle networks the size of the Internet, and the only protocol that can properly handle multiplex connections between unrelated routing domains. BGP builds on the experience of EGP. The main function of BGP system is to exchange network reachable information with other BGP systems. Network reachability information includes information about listed autonomous systems (AS). This information effectively constructs the topology of the AS interconnection and thus clears the routing loop, while policy decisions can be implemented at the AS level.

Characteristics of BGP protocol

BGP is an autonomous system external routing protocol that is used to pass routing information between AS

two。 Path vector routing protocols are designed to avoid loops.

TCP bearer, port number is 179

4. Support for CIDR and route aggregation

5. Routing comes with a wealth of attributes

6. Send only incremental routing updates

7. Route filtering and routing strategy

State transition of BGP Protocol

1. Idle state

Initializes for the initial state when the protocol is activated, resets the timer, and initiates the first TCP connection.

two。 Connection statu

Start a TCP connection and wait for a message that the TCP connection is successful

3. State of action

Attempt to establish a TCP connection

4.open send status

TCP connection has been established, I have sent the first OPEN message, waiting to receive the other party's Open message, and check the message.

5.open confirmed status

BGP waits for the Keepalive message while resetting the hold timer.

6. Connection establishment status

That is, a neighbor (peer) relationship is established, and the router will exchange Update messages with its neighbors and reset the hold timer at the same time.

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