Novell NETWARE 6-DOCUMENTATION Manual page 1878

IP Packet Forwarding Filters
18
Filter Configuration
You can apply IP outgoing filters to RIP, EGP, and OSPF routes. You cannot
filter directly connected networks. The following outgoing IP filters are
available:
RIP outgoing filters restrict the advertising of routing information and
hide the existence of specific IP networks from other routers.
OSPF external route filters define the routes learned from RIP, EGP, or
static routes that are propagated into the OSPF domain.
EGP outgoing filters restrict the routes that are propagated to the EGP
peers.
IP packet forwarding filters let the router filter packets selectively, based on
their source and destination interface fields, the packet type, and the source
and destination address type. The interface can be specified as an interface or
interface type, and the address types can be specified as any address, network,
or host. The packet type is identified by the presence of expected values in the
protocol type field of the IP header and in a protocol-specific operator. Packet
forwarding filters recognize the following protocol types:
Internet Control Message Protocol (ICMP)
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
NetWare Core Protocol (NCP)
The packet type can be further identified by the TCP/UDP port. You can filter
only TCP packets that initiate a connection; therefore, you can restrict access
to TCP services in a specific location while allowing clients in that location to
access outside TCP services.