Author Archive

MVPN

Overview

An SP determines whether a particular VPN is multicast-enabled. If it is, it corresponds to a “Multicast Domain”. A PE which attaches to a particular multicast-enabled VPN is said to belong to the corresponding Multicast Domain. For each Multicast Domain, there is a default “Multicast Distribution Tree (MDT)” through the backbone, connecting [...]

Bidirectional PIM (bidir PIM)

Introduction

RFC5015 specifies Bidirectional PIM (BIDIR-PIM), a variant of PIM Sparse-Mode (PIM-SM) that builds bidirectional shared trees connecting multicast sources and receivers.

The shared tree for each multicast group is rooted at a multicast router called the Rendezvous Point (RP). Different multicast groups can use separate RPs within a PIM domain.

Bidirectional PIM dispenses with both encapsulation [...]

PIM-SSM

IP version 4 (IPv4) addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are designated as source-specific multicast (SSM) destination addresses and are reserved for use by source-specific applications and protocols. For IP version 6 (IPv6), the address prefix FF3x::/32 is reserved for source-specific multicast use.

The SSM destination address 232.0.0.0 is reserved, and it must [...]

Layer 2 Multicast Addresses

Network Interface cards can accept Ethernet frames destined towards the following MAC addresses.

BIA (Mac Address of the NIC)
0xFFFF.FFFF.FFFF (Broadcast Address)
A range of multicast Address

In this post we will discuss the range of multicast addresses.
Ethernet Multicast Addresses

An Ethernet multicast address consists of the

The IANA owned OUI MAC address 01:00:5e (24 bits) – which includes a multicast [...]

Electing an RP (in brief)

The PIMv2 RFC states:
“This specification does not mandate the use of a single mechanism to provide routers with the information to perform the group-to-RP mapping. Currently four mechanisms are possible, and all four have associated problems:

Static Configuration: A PIM router MUST support the static configuration of group-to-RP mappings. Such a mechanism is not [...]

PIM Assert Messages

Where multiple PIM routers peer over a shared LAN, it is possible for more than one upstream router to have valid forwarding state for a packet, which can lead to packet duplication. PIM does not attempt to prevent this from occurring. Instead, it detects when this has happened and elects a single forwarder [...]

Building the shared and shortest path Tree

The Shared tree is rooted at the RP and the shortest path tree is rooted at the Source of the multicast traffic.
The following processes will be discussed.

Building the shared tree between the receivers and the RP
Forwarding unicast PIM Register packets from the source to the RP
Building the shortest Path tree between the RP and the [...]

Pim Packet Formats

The following information was taken from the RFCs below.

RFC 4601(Obsoletes RFC 2362) — Protocol Independent Multicast – Sparse Mode (PIM-SM)
RFC 5059 — Bootstrap Router (BSR) Mechanism for Protocol Independent Multicast (PIM)

To read the RFCs please visit the links below.
ftp://ftp.rfc-editor.org/in-notes/rfc4601.txt
ftp://ftp.rfc-editor.org/in-notes/rfc5059.txt
The following PIM packets formats are described within rfc 4601 and 5059.
RFC 4601 PIM Packet Formats

Hello Message [...]

Multicast posts

In the next few weeks, time permitting I will try and cover the following range of subjects around multicast.

PIM-V2
PIM-SM
PIM-SSM
PIM-bidir
Inter-domain Multicast
MVPN
Inter-As MVPN

To begin with here is a list of some important reserved multicast addresses.

Multicast Address
Usage

224.0.0.1
All Multicast Hosts

224.0.0.2
All Multicast Routers

224.0.0.4
DVMRP Routers

224.0.0.5
All OSPF Routers

224.0.0.6
OSPF Designated Routers

224.0.0.9
RIPv2 Routers

224.0.0.10
EIGRP Routers

224.0.0.13
PIM Routers

224.0.0.22
IGMPv3

224.0.0.25
RGMP

224.0.1.39
Cisco-RP-Announce

224.0.1.40
Cisco-RP-Discovery

Inter-AS Option B – Revisited

Consider the topology below.

Watch the video below or download and watch it on your iphone.