ZyXEL Communications Prestige 861H-G1, Руководство пользователя

Страница: 137 / 275

Prestige 861H User’s Guide
Internet Access 18-3
♦ Out Only
- the Prestige will send out RIP packets but will not accept any RIP packets
received.
♦ None - the Prestige 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
Prestige 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.
18.5.2 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 network-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 Prestige supports both IGMP version 1 (
IGMP-v1 ) and IGMP version 2 ( IGMP-v2 ). At start
up, the Prestige queries all directly connected networks to gather group membership. After that,
the Prestige periodically updates this information. IP multicasting can be enabled/disabled on the
Prestige LAN and/or WAN interfaces in the web configurator (
LAN ; WAN ). Select None to
disable IP multicasting on these interfaces.
18.6 IP Policies
Traditionally, routing is based on the destination address only and the router takes the shortest
path to forward a packet. IP Policy Routing (IPPR) provides a mechanism to override the default
routing behavior and alter the packet forwarding based on the policy defined by the network
administrator. Policy-based routing is applied to incoming packets on a per interface basis, prior
to the normal routing. Create policies using SMT menu 25 (see
IP Policy Routing ) and apply
them on the Prestige LAN and/or WAN interfaces using menus 3.2 (LAN) and 11.3 (WAN).
18.7 IP Alias
IP alias allows you to partition a physical network into different logical networks over the same
Ethernet interface. The Prestige supports three logical LAN interfaces via its single physical
Ethernet interface with the Prestige itself as the gateway for each LAN network.
When you use IP alias, you can also configure firewall rules to control access between the LAN's
logical networks (subnets).
Make sure that the subnets of the logical networks do not overlap.
The following figure shows a LAN divided into subnets A, B, and C.