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Computer Networking : A Top-Down Approach

Computer Networking : A Top-down Approach

Authors:
James F. Kurose, Keith W. Ross
Exercise:
Problems
Chapter:
Security In Computer Networks
Edition:
6
ISBN:
9780132856201
Question:
25

 

Question

Provide a filter table and a connection table for a stateful firewall that is as restrictive as possible but accomplishes the following:

a. Allows all internal users to establish Telnet sessions with external hosts.

b. Allows external users to surf the company Web site at 222.22.0.12.

c. But otherwise blocks all inbound and outbound traffic.

The internal network is 222.22/16. In your solution, suppose that the connec- tion table is currently caching three connections, all from inside to outside. You’ll need to invent appropriate IP addresses and port numbers.

Answer

a,b,c)

The following filter table is used to accepts all internal users to establish Telnet sessions with external hosts and accepts external users to surf the company Web site at 222.22.0.12, but locks all inbound and outbound traffic.

The following connection table is used to verify the connection table to know whether the packet is a part of an ongoing TCP connection or not. If the packet is not a part of connection, then firewall rejects the packet data.

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