ZyXEL Communications ZYWALL10 - Manual (Page 51)

ZyWALL 10 Internet Security Gateway
Internet Access 3-3
Internet addresses for your local networks. On the other hand, if you are part of a much larger organization,
you should consult your network administrator for the appropriate IP addresses.
Regardless of your particular situation, do not create an arbitrary IP address; always
follow the guidelines above. For more information on address assignment, please refer
to RFC 1597, Address Allocation for Private Internets and RFC 1466, Guidelines for
Management of IP Address Space.
3.1.5 RIP Setup
RIP (Routing Information Protocol, RFC1058 and RFC 1389) allows a router to exchange routing
information with other routers. The RIP Direction field controls the sending and receiving of RIP packets.
When set to Both or Out Only, the ZyWALL will broadcast its routing table periodically. When set to
Both or In Only, it will incorporate the RIP information that it receives; when set to None, it will not send
any RIP packets and will ignore any RIP packets received.
The Version field controls the format and the broadcasting method of the RIP packets that the ZyWALL
sends (it recognizes both formats when receiving). RIP-1 is universally supported; but RIP-2 carries more
information. RIP-1 is probably adequate for most networks, unless you have an unusual network topology.
Both RIP-2B and RIP-2M sends the routing data in RIP-2 format; the difference being that RIP-2B uses
subnet broadcasting while RIP-2M uses multicasting. Multicasting can reduce the load on non-router
machines since they generally do not listen to the RIP multicast address and so will not receive the RIP
packets. However, if one router uses multicasting, then all routers on your network must use multicasting,
also.
By default, RIP Direction is set to Both and the Version set to RIP-1.
3.1.6 IP Multicast
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender — 1 recipient) or
Broadcast (1 sender — everybody on the network). Multicast delivers IP packets to a group of hosts on the
network - not everybody and not just 1.
IGMP (Internet Group Multicast Protocol) is a session-layer protocol used to establish membership in a
Multicast group - it is not used to carry user data. IGMP version 2 (RFC 2236) is an improvement over
version 1 (RFC 1112) but IGMP version 1 is still in wide use. If you would like to read more detailed
information about interoperability between IGMP version 2 and version 1, please see sections 4 and 5 of
RFC 2236. The class D IP address is used to identify host groups and can be in the range 224.0.0.0 to
239.255.255.255. The address 224.0.0.0 is not assigned to any group and is used by IP multicast computers.
The address 224.0.0.1 is used for query messages and is assigned to the permanent group of all IP hosts
(including gateways). All hosts must join the 224.0.0.1 group in order to participate in IGMP. The address
224.0.0.2 is assigned to the multicast routers group.
The ZyWALL supports both IGMP version 1 (IGMP-v1) and IGMP version 2 (IGMP-v2). At start up, the
ZyWALL queries all directly connected networks to gather group membership. After that, the ZyWALL
periodically updates this information. IP Multicasting can be enabled/disabled on the ZyWALL LAN and/or