What is IPIP PIM Sparse-Mode command?
ip pim sparse-mode command enables your interface (SVI) to participate in sparse mode multicast traffic transmission and multicast shared tree. this way clients in that VLAN are able to receive multicast traffic from different multicast groups (sources) although you can controll it by configuring other parameters.
What is the difference between PIM Sparse Mode and dense mode?
PIM sparse mode: this is a “pull” model where we only forward multicast traffic when requested. PIM dense mode: this is a “push” model where we flood multicast traffic everywhere and then prune it when it’s not needed. The third one is PIM sparse-dense mode where we can use sparse or dense mode for each multicast group.
What are the different modes of Pim routing?
Topics 1 PIM Sparse Mode. PIM Sparse Mode (PIM-SM) is a multicast routing protocol designed on the assumption that recipients for any particular multicast group will be sparsely distributed throughout the network. 2 PIM Dense Mode. ... 3 Bi-directional PIM. ... 4 Mixed-mode PIM Configurations. ...
When do PIM Sparse routers send a PIM Join message?
To summarize this, PIM sparse routers will send a PIM join message when: The router has received an IGMP membership report from a host on a directly connected interface. The router has received a PIM join from a downstream router. When the RP receives the PIM join, it will start forwarding the multicast traffic.
What are 3 modes in which PIM can operate?
There are three version of IGMP, IGMP Version-1, IGMP Version-2 & IGMP version-3.
What is IP PIM dense mode?
Introduction. Protocol Independent Multicast - Dense Mode (PIM-DM) is a data-driven multicast routing protocol, which builds source-based multicast distribution trees that operate on the Flood- and-Prune principle. It requires unicast-reachability information, but does not depend on a specific unicast routing protocol.
How does multicast sparse mode work?
To solve this issue, PIM sparse mode uses a RP (Rendezvous Point) in the network. Here's how it works: Each router that receives multicast traffic from a source will forward it to the RP. Each router that wants to receive multicast traffic will go to the RP.
What is PIM Sparse Mode vs dense mode?
PIM Sparse Mode (PIM-SM) explicitly builds unidirectional shared trees rooted at a rendezvous point (RP) per group, and optionally creates shortest-path trees per source. PIM-SM generally scales fairly well for wide-area usage. PIM Dense Mode (PIM-DM) uses dense multicast routing.
What is the difference between PIM and IGMP?
IGMP snooping allows a device to only forward multicast streams to the links on which they have been requested. PIM Sparse mode requires specific designated routers to receive notification of all streams destined to specific ranges of multicast addresses.
What is IP PIM passive?
PIM Passive is used to reduce and minimize unnecessary PIM Hello and other PIM control messages. PIM Passive allows you to specify that the interface is "passive" in regards to PIM.
What is the role of the RP in PIM sparse mode?
PIM Sparse Mode uses a special router called a Rendezvous Point (RP) to connect the flow source or multicast tree to the router next to the wannabe receiver. The RP is typically used only temporarily, as we'll see below. There can be different RP's for different multicast groups, which is one way to spread the load.
What is a PIM router?
PIM (Protocol Independent Multicast) is a multicast routing protocol, that is used to send traffic from a single source to multiple destinations across a network. PIM is a collection of three protocols - PIM Sparse Mode, PIM Dense Mode and PIM Bi-directional .
What is IP PIM SSM range?
SSM IP Address Range The Internet Assigned Numbers Authority (IANA) has reserved the address range 232.0. 0.0 through 232.255. 255.255 for SSM applications and protocols. Cisco IOS software allows SSM configuration for an arbitrary subset of the IP multicast address range 224.0. 0.0 through 239.255.
What is IGMP in networking?
The Internet Group Management Protocol (IGMP) manages the membership of hosts and routing devices in multicast groups. IP hosts use IGMP to report their multicast group memberships to any immediately neighboring multicast routing devices.
What is Rp in multicast?
The single tree-based multicast system uses a Rendezvous Point (RP) based message dissemination scheme. That is, a sender of the multicast group sends a message to the root or the RP node of the tree, which then forwards the message along the tree to all receivers.
What is IP multicast routing distributed?
Multicast routing protocols distribute data to multiple recipients. Using IP multicast, a source can send a single copy of data to a single multicast address, which is then distributed to an entire group of recipients.
What does PIM stand for in networking?
Protocol Independent Multicast (PIM) is a collection of multicast routing protocols, each optimized for a different environment. There are two main PIM protocols, PIM Sparse Mode and PIM Dense Mode.
What is the purpose of an RP in PIM?
An RP acts as the meeting place for sources and receivers of multicast data. In a PIM-SM network, sources must send their traffic to the RP. This traffic is then forwarded to receivers down a shared distribution tree.
What is Cisco PIM?
Protocol Independent Multicast or PIM is a group of multicast routing protocols designed for specific network environments. To forward our IP multicast traffic, we need to use a multicast routing protocol. PIM Multicast is the only multicast routing protocol that Cisco IOS devices fully support.
How does PIM SSM work?
PIM operations within the SSM range of addresses change to PIM-SSM, a mode derived from PIM-SM. In this mode, only PIM (S, G) join and prune messages are generated by the router, and no (S, G) rendezvous point tree (RPT) or (*, G) RPT messages are generated.
What is PIM in sparse mode?
A Protocol Independent Multicast (PIM) sparse-mode domain uses reverse-path forwarding (RPF) to create a path from a data source to the receiver requesting the data. When a receiver issues an explicit join request, an RPF check is triggered. A (*,G) PIM join message is sent toward the RP from the receiver's designated router (DR). (By definition, this message is actually called a join/prune message, but for clarity in this description, it is called either join or prune, depending on its context.) The join message is multicast hop by hop upstream to the ALL-PIM-ROUTERS group (224.0.0.13) by means of each router’s RPF interface until it reaches the RP. The RP router receives the (*,G) PIM join message and adds the interface on which it was received to the outgoing interface list (OIL) of the rendezvous-point tree (RPT) forwarding state entry. This builds the RPT connecting the receiver with the RP. The RPT remains in effect, even if no active sources generate traffic.
Why is PIM sparse mode important?
The transitional aspect of PIM sparse mode from shared to source-based tree is one of the major features of PIM, because it prevents overloading the RP or surrounding core links.
How do routers join a PIM sparse mode tree?
Routers with downstream receivers join a PIM sparse-mode tree through an explicit join message.
What happens when the number of PIM join messages exceeds the configured MTU?
If the number of PIM join messages exceeds the configured MTU, the messages are fragmented in IPv6 PIM sparse mode. To avoid the fragmentation of PIM join messages, the multicast traffic receives the interface MTU instead of the path MTU.
How does a PIM join work?
If the RP router has interested receivers in the PIM sparse-mode domain, it sends a PIM join message toward the source to build a shortest-path tree (SPT) back to the source. The source sends multicast packets out on the LAN, and the source DR encapsulates the packets in a PIM register message and forwards the message toward the RP router by means of unicast. The RP router receives PIM register messages back from the source, and thus adds a new source to the distribution tree, keeping track of sources in a PIM table. Once an RP router receives packets natively (with S,G), it sends a register stop message to stop receiving the register messages by means of unicast.
What happens when a PIM register message is received?
If the RP router receives a PIM register message from an active source but has no interested receivers in the PIM sparse-mode domain, it still adds the active source into the PIM table. However, after adding the active source into the PIM table, the RP router sends a register stop message. The RP router discovers the active source’s existence and no longer needs to receive advertisement of the source (which utilizes resources).
Where is the RP router?
The RP router is downstream from the source and forms one end of the shortest-path tree. As shown in Figure 1, the RP router is upstream from the receiver and thus forms one end of the rendezvous-point tree.
Why is PIM sparse mode important?
PIM Sparse Mode is indicated when you need more precise control, especially when you have large volumes of IP multicast traffic compared to your bandwidth. PIM Sparse Mode scales rather well, because packets only go where they are needed, and because it creates state in routers only as needed.
When to use PIM dense mode?
Recall that PIM Dense Mode is used (in principle) when the multicast is desired in most locations. Thus initial multicast packets are flooded everywhere, with pruning cutting off traffic to locations that do not need the multicast feed.
What does a PIM-SM router do when it receives a multicast packet?
When a PIM-SM router receives a multicast packet, it checks the Source Tree for that particular source address and multicast group (destination) address. If there is no entry present, it then checks for a Shared Tree (*, G) entry for the multicast group. If entries are present for both trees, the inbound interface tells the router which tree to use. If both trees have the same inbound interface, then the RP bit for an (S, G) entry prevents duplicate packets: this indicates that the RPF interface lies along the Shared Tree.
How does multicast work with PIM-SM?
The source sends and it is up to the neighboring router (s) to do the right thing. With PIM-SM, the neighboring router knows about the RP. (How it knows is a topic for a whole separate article.) The neighboring router forwards the multicast data to the RP by encapsulating it in a unicast Register message or messages. Normal routing delivers the Register to the RP. The RP de-encapsulates the multicast and forwards copies down any Shared Tree (there is one pre-built if there were receivers Joined up before the Source started sending). If there are receivers (Shared Tree state outbound interfaces), the RP sends a PIM Join back towards the Source. This connects the Source to the RP with a Source Tree, the (S, G) Shortest Path Tree (SPT). Once the RP receives multicasts along this SPT, it sends a Register-Stop to tell the router by the Source to stop sending Register packets. The reason for this behavior is that no multicast packets are lost, if there are receivers already present.
What is a PIM join message?
Recall that a PIM Join message is sent towards a Source (or for PIM-SM, possibly towards an RP), based on unicast routing. The Join message says in effect “we need a copy of the multicasts over here”. It connects the sender of the Join and intervening routers to any existing multicast tree, all the way back to the target of the Join if necessary. A Prune message says in effect “we no longer need this over here”. A router receiving a Prune sees whether it has any other interfaces requiring the multicast flow, and if not, sends its own Prune message. One advanced technique is to arrange a separate and perhaps different copy of the unicast routing information just for multicast purposes. This allows “steering” of the Join messages. MultiProtocol BGP, MBGP, for multicast, is one way to do this (possible later article in the series).
What is the path between the source and the RP?
For a multicast flow with at least one active receiver, the path between the source and the RP will be part of the Source Tree. (Note that “the path between” is a bit vague here, I’m trying to stay away from giving too much detail.)
Do you need to tell each router the RP?
You also need to tell each router the RP, either for all groups or for selected groups (using access lists to specify which RP for which groups). This can be done statically with:
What is PIM sparse mode?
PIM Sparse Mode (PIM-SM) is a multicast routing protocol designed on the assumption that recipients for any particular multicast group will be sparsely distributed throughout the network. In other words, it is assumed that most subnets in the network will not want any given multicast packet. In order to receive multicast data, routers must explicitly tell their upstream neighbors about their interest in particular groups and sources. Routers use PIM Join and Prune messages to join and leave multicast distribution trees.
What is the protocol number for PIM?
All PIM protocols share a common control message format. PIM control messages are sent as raw IP datagrams (protocol number 103), either multicast to the link-local ALL PIM ROUTERS multicast group, or unicast to a specific destination.
What is PIM-DM in network?
PIM Dense Mode (PIM-DM) is a multicast routing protocol designed with the opposite assumption to PIM-SM, namely that the receivers for any multicast group are distributed densely throughout the network. That is, it is assumed that most (or at least many) subnets in the network will want any given multicast packet. Multicast data is initially sent to all hosts in the network. Routers that do not have any interested hosts then send PIM Prune messages to remove themselves from the tree.
How does a router forward data?
When a source first starts sending data, each router on the source's LAN receives the data and forwards it to all its PIM neighbors and to all links with directly attached receivers for the data. Each router that receives a forwarded packet also forwards it likewise, but only after checking that the packet arrived on its upstream interface. If not, the packet is dropped. This mechanism prevents forwarding loops from occurring. In this way, the data is flooded to all parts of the network.
Why do routers use dense mode?
Routers may be configured to use dense mode if the RP discovery mechanism (whatever that may be) fails to find an available RP for a group , and to use sparse or bi-directional mode otherwise.
What is PIM SM?
PIM-SM is a soft-state protocol. That is, all state is timed-out a while after receiving the control message that instantiated it. To keep the state alive, all PIM Join messages are periodically retransmitted. Version 1 of PIM-SM was created in 1995, but was never standardized by the IETF.
When was the Bi-directional PIM protocol developed?
There have been two proposed specifications for Bi-directional PIM. The first was described in draft-farinacci-bidir-pim, which dates from 1999. The protocol described here is a replacement, simpler than and with some improvements over the first. It is described in draft-ietf-pim-bidir.
How to use PIM sparse mode?
When you use PIM sparse mode, our multicast routers need to know where the RP (Rendezvous Point) is in the network and which groups they serve. There are two methods: 1 Static: configure the IP address of the RP on all multicast routers. 2 Dynamic: use Auto RP or BSR.
What is PIM dense mode?
PIM dense mode: this is a “push” model where we flood multicast traffic everywhere and then prune it when it’s not needed.
What does R1 mean in multicast?
R1 is willing to be the RP for the entire 224.0.0.0/4 multicast range. This means that all groups are forwarded with PIM sparse mode.To test if this is true, I will let H1 join a multicast group:
Does sparse mode matter in R2?
For R2, it doesn’t matter if we use sparse or dense mode since it is directly connected to R1. It would have received traffic to 224.1.0.40 anyway. For R3, we do need dense mode since R2 has to flood the traffic it receives from R1 to R3.
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PSA: Catalyst 9300X
NOTE: As of the time of this thread, the Catalyst 9300 Data Sheet have not yet been updated.
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Introduction
Sparse Versus Dense Mode
- Recall that PIM Dense Mode is used (in principle) when the multicast is desired in most locations. Thus initial multicast packets are flooded everywhere, with pruning cutting off traffic to locations that do not need the multicast feed. Until recently, PIM Dense Mode suffered from periodic re-flooding every 3 minutes, but in 12.1(5)T, the PIM Dense Mode State Refresh feature alleviated t…
Basic Rendezvous Point
- We’ve seen so far that PIM-SM uses a Rendezvous Point (RP), to connect source and receivers. There can be only one RP per multicast group, and the simplest implementation uses one RP for all the multicast groups. Let’s talk through the basics of how the RP is used. Let’s assume the source starts sending before there any receivers. If things happen the other way around, some o…
Shared Versus Source Trees
- PIM Sparse Mode (PIM-SM) can use both Shared Trees (passing through the RP) and Source Trees (for efficient direct delivery along the “shortest” path from source to receiver). Typically, it can use both. If efficient delivery is less important to you, and decreasing the amount of state information kept by the routers is more important, then PIM can...
in Conclusion
- Next month we’ll take a look at the various ways of working with Rendezvous Points. We may also touch lightly on a couple of other more advanced IP multicast topics.