The third day of multicast learning and sharing

 

9. multicast forwarding-Multicast Routing Protocol

 

The unicast routing protocol looks at the destination address of the package.

 

The Multicast Routing Protocol depends on where the package comes from. It blocks the loop through RPF reverse route forwarding.

 

RPF is used to determine whether the packet is received by the interface closest to the source --- use the unicast route table to check

 

Note that RPF does not always check the route table using unicast routing, but static multicast routing can be used.

 

The successful RPF packet is forwarded, and the failed RPF packet is quietly discarded.

 

RPF check process

 

Lower AD ---- Longest Match ----- lower metric ---- higher ip

 

Note that there must be only one RPF interface, and the matching process is exactly the opposite to that of the original unicast route.

 

If the router RPF detection fails, it will send the RPF failure message to its upstream device, then the upstream device will no longer send multicast data to this interface

 

Show ip rpf for corresponding viewing

 

When the unicast traffic topology is inconsistent with the multicast traffic topology, the RPF test fails. In this case, ip mroute 10.1.12.0 255.255.255.0 s1

 

In this way, you can manually write multicast routes, affecting RPF detection.

 

Static route AD for multicast is 0-errors and control can be performed based on the RPF detection sequence. You can use the shadow command to adjust the sequence of RPF detection ip mul longest-match to the first normal match. comparison status.

 

10. Conventional multicast Configuration

 

The intermediate router must first enable multicast routing capabilities-ip multicast-routing0

 

If you want to run the multicast routing protocol on all routers in the intermediate network, you must enable the multicast routing protocol under the multicast interface to be sent.

 

The receiver device (router) needs to configure ip igmp join-group 224.1.1.1 (group address) on the multicast network interface)

 

You can use multicast ping on the vro for multicast testing.

 

Debug ip mpacket on the device

 

Note that the default vro enables fast multicast forwarding, so no ip is available on the interface.

 

When Multiple Multicast Routing Protocols exist at the same time, static multicast routing is preferred, DVMRP is preferred, MBGP is preferred, and unicast routing is the last

 

This allows you to view the debug data packets.

 

11. TTL threshold value ---- multicast range control 1

 

Each interface has a TTL value. If the TTL of the multicast packet received is smaller than the TTL of the interface, the packet is discarded.

 

Note that the data packet is sent in the direction, and the TTL must be checked when the data packet is to be sent.

 

Show ip pim f0 detail on the device. The default value is 0.

 

Configure ip mul ttl-threshold 9 in the interface

 

You can set TTL after ping to test

 

12. You can control multicast addresses. The multicast range is 2.

 

Check mul bondary in show ip pim f0 detail to see if it is not set.

 

Ip address of the multicast interface on the device multicast boundary 1

 

1 is the access control list access-list 1 permit 224.1.1.1

 

Define the multicast traffic that can be imported and exported through this interface.

 

This article is from the "Network Technology" blog