BinTec RS353j User Manual page 262

12 Networking
248
A filter describes a certain part of the IP data traffic based on the source and/or destination
IP address, netmask, protocol and source and/or destination port.
You use the rules that you set up in the access lists to tell the gateway what to do with the
filtered data packets, i.e. whether it should allow or deny them. You can also define several
rules, which you arrange in the form of a chain to obtain a certain sequence.
There are various approaches for the definition of rules and rule chains:
Allow all packets that are not explicitly denied, i.e.:
• Deny all packets that match Filter 1.
• Deny all packets that match Filter 2.
• ...
• Allow the rest.
or
Allow all packets that are explicitly allowed, i.e.:
• Allow all packets that match Filter 1.
• Allow all packets that match Filter 2.
• ...
• Deny the rest.
or
Combination of the two possibilities described above.
A number of separate rule chains can be created. The same filter can also be used in dif-
ferent rule chains.
You can also assign a rule chain individually to each interface.
Caution
Make sure you don't lock yourself out when configuring filters:
If possible, access your gateway for filter configuration over the serial console interface
or ISDN Login.
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