PIM for IPv6 Overview
Configuring PIM
page 6-32
OmniSwitch AOS Release 7 Advanced Routing Configuration Guide
March 2011
PIM for IPv6 Overview
IP version 6 (IPv6) is a new version of the Internet Protocol, designed as the successor to IP version 4
(IPv4), to overcome certain limitations in IPv4. IPv6 adds significant extra features that were not possible
with IPv4. These include automatic configuration of hosts, extensive multicasting capabilities, and built-in
security using authentication headers and encryption. Built-in support for QOS and path control are also
features found in IPv6.
IPv6 is a hierarchical 128-bit addressing scheme that consists of 8 fields, composed of 16 bits each. An
IPv6 address is written as a hexadecimal value (0-F) in groups of four, separated by colons. IPv6 provides
3x10^38 addresses, which can help overcome the shortage of IP addresses needed for Internet usage.
There are three types of IPv6 addresses: Unicast, Anycast, and Multicast. A Unicast address identifies a
single interface, and a packet destined for a Unicast address is delivered to the interface identified by that
address. An Anycast address identifies a set of interfaces, and a packet destined for an Anycast address is
delivered to the nearest interface identified by that Anycast address. A Multicast address identifies a set of
interfaces, and a packet destined for a Multicast address is delivered to all the interfaces identified by that
Multicast address. There are no broadcast addresses in IPv6.
The current release also provides support for PIM to be configured in IPv6 environments using IPv6 multi-
cast addresses. In the IPv6 addressing scheme, multicast addresses begin with the prefix ff00::/8. Similar
to IPv6 unicast addresses, IPv6 multicast addresses also have different scopes depending on their prefix,
though the range of possible scopes is different.
Multicast Listener Discovery (MLD) is the protocol used by an IPv6 router to discover the nodes that
request multicast packets on its directly attached links and the multicast addresses that are of interest to
those neighboring nodes. MLD is derived from version 2 of IPv4's Internet Group Management Protocol,
IGMPv2. MLD uses ICMPv6 message types, rather than IGMP message types.
IPv6 PIM-SSM Support
IPv6 Protocol-Independent Multicast Source-Specific Multicast (IPv6 PIM-SSM) is a highly efficient
extension of IPv6 PIM. SSM, using an explicit channel subscription model, allows receivers to receive
multicast traffic directly from the source; an RP tree model is not used. In other words, a Shortest Path
Tree (SPT) between the receiver and the source is created without the use of a Rendezvous Point (RP).
IPv6 PIM software supports Source-Specific Multicast. IPv6 PIM-SSM is automatically enabled and oper-
ational as long as IPv6 PIM is loaded (see
page 6-6
) and PIM sparse mode is enabled with the ssm group
range defined (ip pim ssm group) and IGMPv3 source-specific joins are received within the SSM address
range.
Source-Specific Multicast Addresses
The multicast addresses range FF3x::/32 that has been reserved by the Internet Assigned Numbers Author-
ity (IANA) as Source-Specific Multicast (SSM) destination addresses is not enabled automatically and
must be configured manually to support SSM. Addresses within this range are reserved for use by source-
specific applications and protocols (e.g., IPv6 PIM-SSM) and cannot be used for any other functions or
protocols. However, you can also map additional multicast address ranges for the SSM group.
