Routing
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PIM Bootstrap Router: Candidate Rendezvous Points
A PIM bootstrap router that has been configured as a candidate rendezvous point will receive messages from the bootstrap router. The bootstrap router contains information that will identify the current active bootstrap router. The message can be used for the candidate rendezvous point to forward group to rendezvous point mappings from its cache to the…
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PIM Bootstrap Router
The bootstrap mechanism in a PIM router, is a non-proprietary technology providing a fault tolerant, automated rendezvous point discovery and distribution mechanism. The non-proprietary technology is described in RFC 5059 PIM uses the bootstrap router mechanism to discover and announce rendezvous point information for each group prefix to all routers within a PIM domain. The…
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Rendezvous Point Mapping Agents
A Rendezvous Point Mapping Agent joins the multicast group 224.0.1.39 to receive rendezvous point advertisements. When an announcement has been received, it will store it in a group to rendezvous point mapping cache along with a hold timer. If there are multiple of the same group range advertised, the candidate rendezvous points advertisement with the…
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Candidate Rendezvous Point
A rendezvous point configured as a ‘Candidate Rendezvous Point’ or C-RP, advertises via an RP announcement message that it is willing to become a rendezvous point. The candidate rendezvous point advertises this willingness every 60 seconds by default to the multicast address 224.0.1.39. This is controlled by the rendezvous point announce interval. The announcement message…
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Automatic Rendezvous Point
‘Auto-RP’ is a Cisco propriety technology that automates distribution of multicast group to rendezvous point distribution in a PIM topology. Auto-RP has some benefits: Makes it easier to use multi rendezvous points inside of a network to service different group ranges Allows for load splitting across multiple rendezvous points Simplifies rendezvous point placement towards the…
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Static Rendezvous Point
A rendezvous point can be statically configured on a multicast range by configuring the address of the rendezvous point on every router in the multicast domain. This can be the simplest method of configuring a rendezvous point and is suitable for when there are a low number of routers in the network or if the…
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Rendezvous Points
In PIM Sparse Mode, it is required that one router or more operate as a rendezvous point, or RP. The RP is a single common root placed at a selected point of a shared distribution tree. The RP can be configured statically or learned through a dynamic mechanism. The PIM router can be configured to…
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PIM Assert Mechanism
There can be scenarios in a multicast network where duplicate multicast packets can flow onto the network. There is a mechanism in PIM called the ‘PIM assert mechanism’ that can stop these duplicate flows. This mostly happens in PIM Dense Mode networks due its flooding properties, and rarely happens in PIM Sparse Mode. A PIM…
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Reverse Path Forwarding (RPF)
Reverse Path Forwarding is an algorithm that helps prevent loops and ensures that multicast traffic arrives on the correct interface. The RPF algorithm has several features: When a router receives a multicast packet on an interface that it uses to send unicast packets towards the source, that interface is a RPF interface. When a packet…
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PIM Sparse Mode – Designated Routers
Where there are multiple PIM-SM routers on a subnet, an election is called to determine a designated router (DR). The designated router helps prevent duplicates of multicast traffic from being sent to to the rendezvous point. In an election between PIM sparse mode routers, the highest priority wins the election. By default the priority of…