[hcie discussion] multicast igmp-a

subject 1：1、2、3 What protocols are used for interface No （ Just say the agreement ）, Why do I need to configure this association Please explain in detail （5 branch ）：
answer ：：
Case one ： if PC Support IGMP agreement ,1、2、3 The interface needs to run PIM-SM The protocol and IGMP agreement , Here's why ：
IGMP agreement ：IGMP The protocol is used to realize the management of local group members by multicast devices , The maintenance and management functions of multicast devices are realized by periodically sending universal group query messages .
PIM-SM agreement ： Because there are RP, therefore PIM Model for PIM-SM. Additional operation PIM-SM The reason is that ,PIM The agreement will take advantage of IGMP Arising from the agreement IGMP Group Table items to generate PIM Of （**,G） Table item . When there is multicast traffic , First jump DR Equipment meeting and RP Equipment passing PIM Registration and of the agreement Join Process to build SPT Trees , Finally, two trees are used to guide the traffic for forwarding . According to the topology , There are also several reasons ：
（1）2、3 Interface operation PIM-SM The agreement will be carried out in the early stage DR The election , Only to be DR The device will send R4 send out Join message , Avoid the waste of bandwidth resources caused by sending repeated multicast traffic .
（2）2、3 Interface operation PIM-SM The assertion mechanism will be triggered later in the protocol , Further avoid sending duplicate multicast traffic .
（3）1 No. 1 interface only runs IGMPv2/IGMPv3 You can forward multicast traffic , It's fine too PIM-SM and IGMP The protocols are running .
The benefit of both protocols running is ,PIM-SM The agreement will replace IGMP Arising from the agreement IGMP Routing table , Unified use PIM-SM Agreement table item , Facilitate the later operation and maintenance management .
notes ： If the interface is running IGMPv1, You must run PIM-SM agreement , because IGMPv1 Version does not have its own query election mechanism , Depend on PIM Agreed DR As IGMPv1 The querier for .
The second case ： if PC I won't support it IGMP agreement ,1、2、3 Interfaces should use static grouping and PIM agreement , Here's why ：
function PIM The reason for the agreement is as above , Reasons for configuring static grouping ： To generate static IGMP Table item , send PIM A combination of agreements IGMP Static table item construction （*,G） Table item , And trigger the last jump DR Equipment towards RP Send... In direction Join The message is built along the way （,G） Table item , structure RPT Tree guided multicast traffic forwarding . port 2 And port 3 Assertions are also performed .

subject 2： In large networks RP It's very important , How to guarantee RP The reliability of the , Reduce RP The burden of . Say the specific and feasible methods , And explain why （ Some students are asked to write configuration commands ）（5 branch ）
answer ：
programme 1： Use BSR Dynamic elections RP+ static state RP
stay PIM-SM Multiple are configured in the network C-BSR and C-RP equipment ,C-BSR The equipment will be elected BSR equipment .BSR The device will collect C-RP Device information and generate RP-SET, Send to all multicast routers . The multicast router will use the same algorithm rules to calculate the corresponding group RP. When BSR After the failure , other C-BSR Will choose a new BSR, When RP After the failure , other C-RP Choose a new one RP, So as to achieve RP Backup and improve RP The reliability of the . To further increase RP The reliability of the , You can configure static on each router RP, When in a multicast network BSR Dynamic due to failure RP When the failure , At this time, it is static RP Will replace dynamic RP（ dynamic RP Better than static RP） To ensure the normal operation of the multicast network .
Key configurations are as follows ：

[huawei]multicast routing-enable  // Configure multicast routing function 
[Huawei-loopback0]pim sm  // Turn on PIM-SM agreement （ Become C-BSR/C-RP All devices need to be enabled PIM-SM agreement ）
[Huawei]pim  // Get into PIM View 
[Huawei-pim]c-bsr loopback0 // Set the interface as C-BSR
[Huawei-pim]c-rp loopback0 // Set the interface as C-RP
[Huawei-pim]static-rp x.x.x.x // x.x.x.x For manually set static RP Address 

programme 2： Deploy Anycast RP
stay PIM-SM Deploy within the domain Anycast RP, That is, define multiple in the multicast domain RP（ In a different layer 3 network ）, these RP Have the same IP Address , Thus, the multicast source can register nearby and the receiver can join nearby , Alleviates single RP The burden of RP Backup of , Optimized forwarding path .Anycast RP The deployment of can adopt MSDP and PIM-SM Two solutions .MSDP Our solution uses MSDP Conversation in RP Inter transmission （S,G） Information about , It can be applied to complex multicast environments within or between domains . PIM-SM Our solution does not require the use of MSDP agreement , Apply to any PIM-SM Network scene , The disadvantage is that PIM-SM Our solution requires all RP Establish a fully interconnected neighbor relationship between devices , In large networks, it may lead to too many sessions .
Key configurations are as follows （ With PIM-SM The solution, for example ）：

[huawei]multicast routing-enable  // Enable multicast routing function 
[huawei]pim // Get into pim View 
[Huawei-pim]anycast-rp 1.1.1.1  // To configure anycast rp Address 
[Huawei-anycast-rp-1.1.1.1]local-address 10.1.1.1 // To configure anycast  Local address 
[Huawei-anycast-rp-1.1.1.1]peer 10.1.2.2  // To configure anycast  Neighbor address 

programme 3： Turn on SPT Switch down RP burden
stay PIM-SM In the model , All multicast traffic needs to go through RP Forward . In the network environment with large multicast traffic , Will cause RP Heavy burden , also RP It will also become the bottleneck of the network . In the configuration SPT After switching , When the received multicast traffic exceeds the set value , The equipment will according to its own （S,G） Table item , To the source DR send out join message , At the same time build SPT Trees , Multicast traffic follows SPT Tree for forwarding , No longer passed RP, Thus reducing RP The pressure of the .
Key configurations are as follows ：

[huawei]pim
[Huawei-pim]spt-switch-threshold xxx  // To configure SPT Switching threshold