Security
1.The rule you want to implement as a filter is:
Block all Telnet attempts that originate from the remote host 199.211.211.17.
2.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 determines 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 Dest IP Addr could have been anything. The mask for Source IP Addr must be 255.255.255.255 since an exact match is desired.
•Source IP Addr = 199.211.211.17
•Source IP address mask = 255.255.255.255
•Dest IP Addr = 0.0.0.0
•Destination IP address mask = 0.0.0.0
3.Using the tables on page
•Proto = TCP (or 6)
•D. Port = 23
4.The filter should be enabled and instructed to block the Telnet packets containing the source address shown in step 2:
•On? = Yes
•Fwd = No
This
Source IP | Dest IP | ||||
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1 | 192.211.211.17 | 0.0.0.0 | TCP 0 | 23 | Yes No |
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Filtering example #2
Suppose a filter is configured to block all incoming IP packets with the source IP address of 200.233.14.0, regardless of the type of connection or its destination. The filter would look like this:
Source IP | Dest IP | |||
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1 | 200.233.14.0 | 0.0.0.0 | 0 | Yes No |
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This filter blocks any packets coming from a remote network with the IP network address 200.233.14.0. The 0 at the end of the address signifies any host on the class C IP network 200.233.14.0. If, for example, the filter is applied to a packet with the source IP address 200.233.14.5, it will block it.
