Novell NETWARE 6-DOCUMENTATION Manual page 1882

Zone-Based Outgoing Route Filters
Network Number-Based Outgoing Route Filters
AppleTalk Incoming Route Filters
22
Filter Configuration
Zone-based outgoing route filters limit the advertisement of all routes
associated with a particular zone. A zone is an abstraction of networks into
which many physical networks, including noncontiguous networks, can be
grouped. The main advantage of using zone names in filters is that the filter
does not need to be modified when new networks are added to the zone.
For example, when filters are configured for the Marketing zone, the zone is
made up of only one physical network. As the department grows, more
physical networks are added, but they are still grouped under the Marketing
zone. All filters configured for the Marketing zone are enforced automatically
for all new physical networks added to the zone. This capability greatly
simplifies network management.
NOTE:
When you specify a zone from a network that has multiple zones, all set
filters affect the entire network, not just the selected zone.
Network number-based outgoing route filters limit the advertisement of the
routes to specific networks. This kind of filtering gives very explicit control to
the user about which physical network should or should not be advertised to
different neighbors.
You must reconfigure network number-based outgoing route filters when
changes occur in the network topology.
AppleTalk incoming route filters limit the routing information that a router
accepts and adds to its routing tables.
When these filters are enabled on a router, the router accepts only the allowed
routes from each of its neighboring routers so that specified routes are hidden
from particular routers and from particular parts of the network. Novell
Internet Access Server 4.1 supports only network number-based incoming
route filters.
An incoming route filter consists of a route and the interface through which
the route advertisements are expected to be transmitted. The specified route
can be to a nonextended network or to an extended network.
Directly connected networks cannot be filtered by incoming route filters. If the
specified action is to deny routes in the filter list, the router ignores all the