Earning your CCNA Security certification is a tremendous boost to your career and career prospects! To help you prepare for total success on test day, here are 10 supplemental questions about the IOS Firewall suite. The answers are at the end of the article. Enjoy!
1. Define the term “DMZ” as it relates to network security and name three different common network devices that are typically found there.
2. Identify true statements.
A. Stateless packet filtering considers the state of the TCP connection.
B. Stateful packet filtering considers the state of the TCP connection.
C. Neither stateless nor stateful packet filtering monitors the state of the TCP connection.
D. Both stateless and stateful packet filtering monitor the state of the TCP connection and maintain a state table containing that information.
3. Does the Cisco IOS Firewall feature set act as a stateful or stateless packet filter?
4. Which of the following are considered part of the IOS Firewall feature set?
A.IOS Firewall
B. Intrusion prevention system
C.RADIO
d. Authentication proxy
E. Password encryption
5. Identify the true statements regarding the authentication proxy.
A. It is part of the IOS firewall feature set.
B. Allows the creation of security profiles per user, instead of more general profiles.
C. Allows the creation of general security profiles, but not profiles per user.
D. Profiles can be stored locally, but not remotely.
E. Profiles can be stored on a RADIUS server.
F. Profiles can be stored on a TACACS+ server.
6. Configuring ACLs is an important part of working with the IOS Firewall. What wildcard masks are replaced in ACLs by the words host and any?
7. What does the dollar sign indicate in the following ACL line?
R1(config)#$ 150 deny ip 172.50.50.0 0.0.0.255 172.50.100.0 0.0.0.255
8. Basically, how does an IOS Firewall prevent a TCP SYN attack?
9. What does the term “drill a hole in the firewall” refer to? (Logically, that is, not physically).
10. What exactly does the router traffic option do in the following configuration?
R4(config)#ip inspect name PASSCCNASECURITY tcp router-traffic
R4(config)#ip inspect name PASSCCNASECURITY udp router-traffic
R4(config)#ip inspect name PASSCCNASECURITY icmp router-traffic
Here are the answers!
1. It’s easy to think of your network as “in” and everything else as “out.” However, we do have a third area when it comes to firewalls: the DMZ.
From an IT standpoint, the DMZ is the part of our network that is exposed to external networks. It is common to find the following devices in a DMZ:
FTP server
email server
ecommerce server
DNS servers
web servers
2. (B.) Stateful packet filtering monitors the state of the connection, and that’s particularly important when it comes to preventing TCP attacks. A stateful firewall will not only monitor the state of the TCP connection, but also the sequence numbers. Stateful firewalls accomplish this by maintaining either a session table or a state table.
3. The Cisco IOS Firewall is a stateful filter.
4. (A, B, D.) There are three main components to the IOS firewall feature set: the IOS firewall, the intrusion prevention system (IPS), and the authentication proxy.
5. (A, B, E, F. The Authentication Proxy allows us to create security profiles that will be applied per user, rather than per subnet or per address. These profiles can be maintained in one of the following:
radio server
TACACS+ server
After successful authentication, the security policy for that particular user is downloaded from the RADIUS or TACACS+ server and applied by the router’s IOS Firewall.
6. We have the option of using the word host to represent a wildcard mask of 0.0.0.0. Consider a configuration where only packets from source IP 10.1.1.1 are allowed and all other packets are denied. The following ACLs do that.
R3#conf t
R3(config)#access-list 6 permission 10.1.1.1 0.0.0.0
R3(config)#conf t
R3(config)#access-list 7 permission host 10.1.1.1
The any keyword can be used to represent a wildcard mask of 255.255.255.255. The next two lines allow all traffic.
R3(config)#access-list 15 allow any
R3(config)#access-list 15 permission 0.0.0.0 255.255.255.255
There is no “right” or “wrong” decision to make when configuring ACLs in the real world. However, for your examination, you would be very familiar with the proper usage of host and any.
7. The dollar sign simply indicates that part of the command you are entering or viewing cannot be displayed because the input is too long. It does not mean that the order is illegal.
8. The IOS Firewall can use any or all of the following values to detect when a TCP SYN attack is taking place:
Grand total of incomplete TCP sessions
Number of incomplete TCP sessions in a given period of time
Number of incomplete TCP sessions per host
When any of these thresholds are reached, any of the following actions can be taken:
Block all incoming SYN packets for a certain period of time
Transmit an RST to both parties in the oldest incomplete session
We’ll look at specific instances in future tutorials.
9. That term simply refers to configuring the firewall to open a port that was previously closed. Don’t forget to close it when you no longer need it to be open!
10. If you are going to inspect the traffic that is actually generated by the router, you must include the router traffic option at the end of that particular ip inspection statement.
Find more Cisco certification practice exams and fully illustrated tutorials on my website!