Allied Telesis AR400 SERIES Software Release 2.7.1 - Manual (Page 103)

Routing 103
Software Release 2.7.1
C613-02021-00 REV F
You will see the login screen for the Remote Office router. To connect from
the Remote Office router to the Head Office router, on the Remote Office
router, enter the command:
TELNET 172.16.8.33
5. Save the configuration
To save the new dynamic configuration as a script, enter the command:
CREATE CONFIG=IPCONF.SCP
Configuring IP Multicasting
IP multicasting is used to transmit packets to a group of hosts simultaneously
on a TCP/IP network or sub-network. Network bandwidth is saved because
files are transmitted as one data stream and are split apart by the router to the
target stations at the end of the path.
The multicast environment consists of senders (IP hosts), routers and switches
(intermediate forwarding devices) and receivers (IP hosts). Any IP host can
send packets to a multicast group, in the same way that they send unicast
packets to a particular IP host, by specifying its IP address. A host need not
belong to a multicast group in order to send packets to the multicast group.
Packets sent to a group address are only received by members of the group.
For multicasting to succeed, the router needs to know which of its interfaces
are directly connected to members of each multicast group. To establish this,
the router uses Internet Group Management Protocol (IGMP) for multicast
group management. IGMP is used between hosts and multicast routers and
switches on a single physical network to establish hosts’ membership in
particular multicast groups.
The router uses this information, in conjunction with a multicast routing
protocol, to know which other routers to route multicast traffic to. The router
maintains a routing table for multicast traffic with Distance Vector Multicast
Routing Protocol (DVMRP), Protocol Independent Multicast-Sparse Mode
(PIM-SM), or Protocol Independent Multicast-Dense Mode (PIM-DM). You
must configure IGMP and one of the multicast routing protocols before the
router can forward multicast packets. DVMRP and PIM-Sparse Mode share a
separate multicast forwarding table.
When the router receives a packet addressed to a multicast group, it forwards it
to the interfaces that have group members connected to them, according to
IGMP, and out other interfaces specified by the multicast routing protocol.
Membership in a multicast group is dynamic; hosts can join and leave at any
time. Multicast groups can be long or short lived, and can have relatively stable
or constantly changing membership. There is no limit on the location or
number of members in a multicast group. A host can belong to more than one
multicast group at a time.
When the router finds out from IGMP that a new host has joined a multicast
group on one of its interfaces, the router needs to receive the multicast traffic
for this group, so that it can forward it to the host. The router uses the multicast
routing protocol (DVMRP, PIM-SM or PIM-DM) to notify routers closer to the
sender (upstream) to forward it traffic for the group.
While you can configure different multicasting protocols on different interfaces
on the same router, multicasting information is not translated between the
different multicast protocols.