Behavior Of Group Members Among Older Version Group Members; Behavior Of Multicast Routers Among Older Version Queriers; Behavior Of Multicast Routers Among Older Version Group Members; Describing The Xsr's Pim-Sm V2 Features - Enterasys Security Router X-PeditionTM User Manual

Behavior of Group Members Among Older Version Group Members

An IGMPv3 host may be situated in a network where hosts have not yet been upgraded to
IGMPv3. A host may allow its IGMPv3 Membership Record to be suppressed by either a Version 1
or Version 2 Membership Report

Behavior of Multicast Routers Among Older Version Queriers

IGMPv3 routers may be sited on a network where at least one router on the network has not yet
been upgraded to IGMPv3 with these requirements:
• If older versions of IGMP exist on routers, the querier must use the lowest IGMP version
present on the network. This must be assured administratively; routers that desire to be
compatible with IGMPv1 and IGMPv2 must have a configuration option to act in IGMPv1 or
IGMPv2 compatibility modes which can be set with the
in IGMPv1 mode, routers must send Periodic Queries with a Max Resp Code of 0 and truncated
at the Group Address field (i.e., 8-bytes long), and must ignore Leave Group messages. They
should also log receipt of IGMPv2 or IGMPv3 queries. When in IGMPv2 mode, routers must
send Periodic Queries truncated at the Group Address field (i.e., 8-bytes long), and should
also log receipt of IGMPv3 queries. They also must fill in the Max Resp Time in the Max Resp
Code field; that is, the exponential algorithm described is not used.
• If you do not explicitly configure a router to use IGMPv1 or IGMPv2 and it receives an
IGMPv1 Query or IGMPv2 General Query, it should log a warning.

Behavior of Multicast Routers Among Older Version Group Members

IGMPv3 routers may be placed on a network where there are hosts that have not yet been
upgraded to IGMPv3 but for compatibility with older version hosts, IGMPv3 routers must operate
in version 1 and version 2 compatibility modes. IGMPv3 routers keep a record of compatibility
mode by group, which is determined by the Group Compatibility Mode variable from one of three
states: IGMPv1, IGMPv2 or IGMPv3. This variable is kept per group record and is dependent on
the version of Membership Reports heard for that group as well as the Older Version Host Present
timer for the group.

Describing the XSR's PIM-SM v2 Features

PIM-SM is a sparse-mode multicast routing protocol that uses a receiver-initiated process to build
and maintain the MDT, as specified in draft-ietf-pim-sm-v2-new-05. A router running PIM-SM joins
the construction of a MDT only when at least one of the hosts on its subnet requests membership
in the specific multicast group. PIM-SM supports both shared and shortest-path trees (SPT) and
can convert from shared to shortest-path tree based on network status to optimize multicast
performance.
PIM-SM relies on another protocol to discover and collect network topology data and fill the
Multicast Routing Information Base (MRIB). The MRIB is used by PIM-SM to learn how to reach
other PIM-SM enabled routers. MRIB can derive from the unicast routing table filled by unicast
routing protocols, such as RIP and OSPF, or it can be filled by another routing protocol tailored for
multicast, such as MBGP. MRIB is also used to check against incoming multicast packets to ensure
loop-free forwarding.
PIM-SM behavior can be described in three phases. Since senders and receivers can join or leave at
any time, all phases may occur in parallel.
Describing the XSR's PIM-SM v2 Features
ip igmp version command. When
XSR User's Guide 7-7