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Problems caused by traditional VPN 1. Too many VPNs make maintenance difficult and take up more equipment performance 2. VPN cannot achieve dynamic switching 3. Suitable for small-scale VPN networks DMVPN Dynamic Multipoint VPN, is a Cisco private VPN GRE Generic Routing Encapsulation GRE general routing encapsulation can support common routing protocols. In essence, it establishes a tunnel, which can transmit a variety of traffic. Advantages:  Support multiple protocols, transmit multiple flows ipv4 ipv6 Disadvantages : just provide a tunnel to ensure specificity. GRE OVER IPSec DMVPN has the advantages and disadvantages of GRE VPN DMVPN + IPSec VPN   The essence of DMVPN: rely on the routing table to decide who to establish a VPN with DMVPN: set up in a dynamic way. For a tunnel, the key parameters to establish a tunnel are the tunnel's source address and the tunnel's destination address. MGRE: Multiple VPNs can be established under one inter...

LDP neighbor establishment 1. Neighbor discovery stage:   Use UDP packets Both source and destination ports are UDP 646 R1#show mpls ldp discovery Verifies whether the other party's LDP hello is received 2. The session establishment phase: Using TCP messages, unicast one-to-one. By default, the largest transport-address is the initiator. The default transport-address is equal to router-id router-id and ospf router-id election are the same [manual election & automatic election] Ensure that the transport-address address is reachable   ① Run IGP protocol ② Manually specify the physical address as router-id Use the following commands to modify the transport-address in interface mode   (Config-if)#mpls ldp discovery transport-address interface【Specify the current interface】 (Config-if)#mpls ldp discovery transport-address x.x.x.x [specify the transport-address separately] LDP protocol configuration basic commands ip CEF [The router op...

SMTP   is a protocol that provides reliable and effective email transmission. SMTP is a mail service built on the FTP file transfer service. It is mainly used for the transfer of mail information between systems and provides notifications about incoming mail. SMTP is independent of a specific transmission subsystem and only requires reliable and orderly data flow channel support. One of the important characteristics of SMTP is that it can transmit mail across the network, that is, "SMTP mail relay". Using SMTP, you can achieve mail transmission between the same network processing process, and you can also use a relay or gateway to achieve mail transmission between a processing process and other networks. SMTP is a relatively simple text-based protocol. One or more recipients of a message are specified on it, and then the message text is transmitted. In the early 1980s, SMTP began to be widely used. At the time, it was just a supplement to UUCP, which was more suitable fo...

Today I will talk about Cisco CGMP and RGMP. CGMP protocol, Cisco group management protocol: CGMP is used to limit multicast traffic on Layer 2 networks. Because the switch cannot view Layer 3 data packets, and cannot distinguish between IGMP packets. With CGMP, the router tells the switch the interface of the multicast group users that only the router can generate CGMP packets, and the switch just listens for CGMP packets. Mainly provide the following services: 1. Allow IP multicast packets to be switched to those ports that have IP multicast clients. 2. Keep the network bandwidth in the user field so that unnecessary IP multicast traffic will not be relayed. 3. No additional overhead is incurred when creating a separate VLAN for each multicast group in the switched network. CGMP has two types of data packets: Join The router announces to the switch to add a member to the multicast group Leave The router informs the switch to delete a member from the multicast...

I saw that there are various protocols written in some message format encyclopedias, but there is no protocol for these dialogues. Is it because they belong to different levels? However, there are also some application layer protocols such as SNMP. Is it the difference between routing protocols? Learning these knowledge points of computer network does not depend on different types of memories, but on understanding. If you understand it, you don’t need to remember it. You remember that HTTPS belongs to the application layer, but you are deceived by books, because this world has no HTTPS protocol at all, and this world only has TLS security protocol and HTTP protocol! TLS is equivalent to security personnel. It is responsible for escorting HTTP materials. When the safety reaches the destination, the security personnel are naturally redundant. Go back to your home, and find your mom. The destination receiver only cares about the transportation material itself, but has no interest i...

Of course, the home network, enterprise network, and data center are connected to the operator's access network through optical fiber. The trickle flows from the access network are aggregated into super-large traffic, which is transmitted to the core switching network using higher-speed optical fiber links, where it is distributed to all corners of the world according to the destination of the traffic. The popular science articles that we often see on the Internet, the pictures that see the Internet usually look like this: After reading these pictures, I still can't understand how the Internet is connected. To understand the local connection information, you can refer to this picture: Each Backbone in the picture can represent an operator. You can think of them as "China Telecom", "China Unicom", and "China Mobile". Each operator, like an independent kingdom, uses an AS number to exchange global routing tables with other kingdoms. In t...