Principles of RPF check on the AR router

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In unicast routing and forwarding, unicast packets are transmitted along a P2P path. The router only needs to consider the destination address, so it can learn the outbound interface through which a packet can be forwarded to the destination. Multicast routing and forwarding are different. The destination address of multicast packets is the multicast address that just identifies a group of receivers. That is, the receiver's position cannot be found based on the destination address. However, the source address of multicast packet is determined. Therefore, the correctness of forwarding path of multicast packets depend on the source address.
When a router receives a multicast packet, it searches the unicast routing table for the route to the source address of the packet. After finding the route, the router checks whether the outbound interface of the route is the same as the inbound interface of the multicast packet. If they are the same, the router considers that the multicast packet is received from a correct interface. This ensures correctness and uniqueness of the entire forwarding path. This process is called RPF check.
The correct interface is called an RPF interface.

Other related questions:
WLAN support on the AR router
Definition: A wireless local area network (WLAN) is a network that uses wireless channels such as radio waves, laser, and infrared rays to replace the transmission media used on a wired LAN.WLAN technology described in this document is implemented based on 802.11 standards. That is, a WLAN is a network that uses high-frequency signals (for example, 2.4 GHz or 5 GHz signals) as transmission media. 802.11 was originally a wireless LAN communications standard defined by the Institute of Electrical and Electronics Engineers (IEEE) in 1997. The IEEE then made amendments to the standard, forming the 802.11 family, including 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11i, and 802.11n. Purpose: Wired LANs use wired cables or optical fibers as transmission media, which are expensive and have fixed locations. As people have increasing requirements on network mobility, wired LANs cannot meet these requirements. WLAN technology is then developed. Currently, WLAN has become a cost-efficient network access mode. WLAN technology allows you to easily access a wireless network and move around within the coverage of the wireless network. Benefit: - High network mobility: WLANs can be connected easily, which is not limited by cable and port positions. WLANs especially apply to scenarios such as office buildings, airport halls, resorts, hotels, stadiums, and cafes. - Flexible network deployment: WLANs can provide wireless network coverage in places where cables are difficult to deploy, such as subways and highways. This solution reduces cables, offers ease of implementation at a low cost, and has high scalability. For details, see WLAN-AC Configuration Guide .

Principles of HSB
The AR supports the HSB function. HSB implementation involves data synchronization and traffic switching. Data synchronization is performed to ensure consistent information on the master and backup devices when the two devices are working normally. Traffic switching is performed to ensure non-stop service forwarding when the master device fails or recovers. The principle for data synchronization is to establish active and standby channels between devices that back up each other. Session entries of the master device can be synchronized to the backup device through the channel at one time, in real time, or periodically. The principle for traffic switching is based on negotiation between the master device and the backup device using VRRP. When the master device fails, a new master device is elected based on VRRP priorities and the traffic is switched to the master device. For details, see “HSB Configuration�?in AR100&AR120&AR150&AR160&AR200&AR1200&AR2200&AR3200&AR3600 V200R008 CLI-based Configuration Guide - Reliability.

What is the function of MBGP
In MSDP, the unicast route for the RPF check can be an IGP route or a BGP route. MBGP only separates the unicast routing table and the multicast routing table through the related address family to support different unicast topologies and multicast topologies. Unicast and multicast can adopt the same topology.

How do I view the broadband account of the AR router
Run the display current-configuration command to check the configuration file of the AR router. 1. When the AR router functions as the PPPoE server and "local-user user1@system service-type ppp" is queried, user1@system is the user name of the local account. 2. When the AR router functions as the PPPoE client and "ppp chap user user1@system" or "ppp pap local-user user1@system password" is queried, user1@system is the user name of the local account.

How to check the configuration of the interface of an AR router
You can run the following commands to check the basic parameter configuration of an interface: - Run the display interface command to check the current running status of the interface, including the running status and basic configuration of the interface and the status of the packets forwarded by the interface. - Run the display interface brief command to check brief information about the status and configuration of the interface, including the physical state and protocol state of the interface, bandwidth utilization rate in transmitting and receiving directions in the recent period, and the number of error packets that are sent and received. - Run the display ip interface command to check the main configuration of the interface. - Run the display default-parameter interface command to check the default configuration of the interface. - Run the display interface description command to check the description of the interface. - Run the display interface counters { inbound | outbound } command to check the statistics of the packets sent or received by the physical interface.

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