Filtering example #1 – Netopia 2200 User Manual
Page 160
160
•
Fwd: Shows whether the filter forwards (Yes) a packet or discards (No) it when there’s
a match.
•
Src-IP: The packet source IP address to match.
•
Src-Mask: The packet source subnet mask to match.
•
Dst-IP: The packet destination IP address to match.
•
Dst-Mask: The packet destination IP address to match.
•
Protocol: The protocol to match. This can be entered as a number (see the table
below) or as TCP or UDP if those protocols are used.
•
Src Port: The source port to match. This is the port on the sending host that originated
the packet.
•
Dst Port: The destination port to match. This is the port on the receiving host for which
the packet is intended.
•
NC: Indicates No Compare, where specified.
Filtering example #1
Returning to our filtering rule example from above (see
), look at how a rule is
translated into a filter. Star t with the rule, then fill in the filter’s attributes:
•
The rule you want to implement as a filter is:
“Block all Telnet attempts that originate from the remote host 199.211.211.17.”
•
The host 199.211.211.17 is the source of the Telnet packets you want to block, while
the destination address is any IP address. How these IP addresses are masked deter-
mines what the final match will be, although the mask is not displayed in the table that
displays the filter sets (you set it when you create the filter). In fact, since the mask for
the destination IP address is 0.0.0.0, the address for Destination IP address could
have been anything. The mask for Source IP address must be 255.255.255.255 since
an exact match is desired.
Protocol
Number to use
Full name
N/A
0
Ignores protocol type
ICMP
1
Internet Control Message Protocol
TCP
6
Transmission Control Protocol
UDP
17
User Datagram Protocol