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:


  1. What Are Filters?

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:

  1. IP source address (IP address mask, IP address)
  2. IP destination address (IP address mask, IP address)
  3. Protocol
  4. 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.

  1. How to Configure Filter Sets
  1. Open the IRT-401 NMS program and logon to the router.
  2. Click on the Local Tab. In the Local page, click the IP tab.
  3. Figure 10-1. The Local / IP Page.

  4. In the Access List area on the bottom half of the IP page, click the "Add" button. You will see the Operation on Access List window.
  5. Figure 10-2. The Operation on Access List Window.

  6. Configure filter as desired.
  7. Click "OKto register your entry. To enter more filters, repeat steps 3 through 5.
  8. Each filter entry has an independent action field. If you choose "deny", then the setting will have limited forwarding via the IRT-401. If you choose "accept", the setting will not be limited.
  9. If you want to edit an entry, click on the entry, then click "Modify".
  10. When you have added all of the desired filter sets, click "Update" to save the information. You have now completed adding a filter set.




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Copyright (C) 1999 PLANET Technlogy Corporation