User's Manual for
PLANET ISDN Router Product
IRT-401
Chapter 10. Setting Up Data Filters
This chapter provides a brief introduction to filters and instructions on how to configure your IRT-401 to use them.
Topics covered:
The IP packet filters specify IP packet-screening criteria used to filter IP traffic. You can create up to 8 IP packet filters. For every received IP packet not destined for the router itself, your IRT-401 checks the packet content against the existing IP packet filters one by one. If any one of the filters describes (i.e. matches) the received packet, the action "accept" (i.e. forward) or "deny" (i.e. discard) associated with the filter is applied to the packet, otherwise the packet is forwarded by default.
An IP packet filter specifies and checks the following 4 attributes:
- IP source address (IP address mask, IP address)
- IP destination address (IP address mask, IP address)
- Protocol
- Port number
An IP packet filter describes an IP packet if all 4 attributes evaluated match against the received IP packet. The associated action will be applied to the described packets.
IP source address, IP destination address
The following logic is evaluated against both IP source and destination addresses.
The packet's IP address is first "AND" with the IP address mask specified in the filter. This attribute is considered a match if the AND-operation result equals the IP address specified in the filter.
For example:
An IP destination address attribute with
Destination IP mask = 255.255.255.255, and
Destination IP address = 192.31.7.130
Will match all IP packets with destination IP address = 192.31.7.130.
An IP source address attribute with
Source IP mask = 255.255.255.0, and
Source IP address = 192.168.0.0
Will match all IP packets with source IP address = 192.168.0.0 ~ 192.168.0.255.
Protocol
The protocol here means some of the well-known TCP/IP transport layer protocols such as ICMP used by "ping", TCP used by FTP, WWW, and UDP used by SNMP. This attribute is considered a match if the protocol specified in the filter equals the protocol field carried by the received IP packet. If the protocol = all, then the attribute protocol is an automatic match.
Port Number
Port Number here means the transport layers port number. This attribute is considered a match if the port number specified in the filter is equal to the source port numbers destination port number carried in the received IP packet. If the port number = 0, then the attribute port number is automatically matched.
Figure 10-1. The Local / IP Page.
Figure 10-2. The Operation on Access List Window.
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Copyright (C) 1999 PLANET Technlogy Corporation