What is the difference between a vro and a local loop?

Loop interfaces are logical interfaces, that is, virtual software interfaces. They are not real router interfaces, in ospf, the loopback interface is configured to ensure that there is always an active interface in the ospf process. the loopback interface can be used for ospf configuration and diagnosis. If you do not configure the loopback interface, the highest IP address on the router will become the router ID of the router, this vroid ID is used to advertise the route and elect the specified vro and backup the specified vro.

1. 127.0.0.1 is usually called the local loopback address. It represents the local Virtual Interface of the device, so it is regarded as an interface that will never go down by default, therefore, you can ping the local loopback address before installing the NIC. Generally, it is used to check whether the local network protocol, the IP stack inside the system, and the basic data interface of the filtered advertisement are normal.

2. As the management address of a vroback, after the system administrator completes the network planning, a loopback interface is created for each vro for convenient management, you can specify an IP address as the management address on this interface. The Administrator uses this address to remotely log on to the vrotelnet (telnet). This address actually provides a function similar to a device name.

3. There are usually many interfaces and addresses on each vro. Why don't you choose one of them? Because the telnet command uses TCP packets, the following situation may occur: A router interface is down due to a fault, but other interfaces can still be telnet, that is, the TCP connection to this vro still exists. Therefore, the selected telnet address must never be down, and the virtual interface meets this requirement. Because this type of interface does not require interconnection with the peer end, the address of the loopback interface is usually specified as a 32-bit mask to save address resources.

4. Use this interface address as the router id of the Dynamic Routing Protocol OSPF and BGP. During the operation of the Dynamic Routing Protocol OSPF and BGP, you must specify a Router id for the Protocol, it is the unique identifier of the vro and must be unique within the autonomous system. The router id is a 32-bit unsigned integer, which is very similar to the IP address. In addition, the IP address is not repeated, so the router id is usually specified as the address of an interface on the device. Because the IP address of the loopback interface is generally regarded as the router id, it is the best choice for the router id.

Use this interface address as the source address for establishing a TCP connection with BGP. In the BGP protocol, the two routers that run BGP establish a neighbor relationship through TCP, when configuring a neighbor, the loopback interface is often specified as the source address for establishing a TCP connection.