CCNA – Access List Simulation 2

A network associate is adding security to the configuration of the Corp1 router. The user on host C should be able to use a web browser to access financial information from the Finance Web Server. No other hosts from the LAN nor the Core should be able to use a web browser to access this server. Since there are multiple resources for the corporation at this location including other resources on the Finance Web Server, all other traffic should be allowed.

The task is to create and apply an access-list with no more than three statements that will allow ONLY host C web access to the Finance Web Server (172.22.242.23). No other hosts will have web access to the Finance Web Server. All other traffic is permitted.

CISCO CCNA Exam – Q337

Answer and Explanation:

Corp1>enable (you may enter “cisco” as it passwords here)

We should create an access-list and apply it to the interface which is connected to the Server LAN because it can filter out traffic from both Sw-2 and Core networks. The Server LAN network has been assigned addresses of 172.22.242.17 – 172.22.242.30 so we can guess the interface connected to them has an IP address of 172.22.242.30 (.30 is the number shown in the figure). Use the “show ip interface brief” command to check which interface has the IP address of 172.22.242.30.
CISCO CCNA Exam – Q337b

We learn that interface FastEthernet0/1 is the interface connected to Server LAN network. It is the interface we will apply our access-list (for outbound direction).

Corp1# configure terminal

Our access-list needs to allow host C – 192.168.33.3 to the Finance Web Server 172.22.242.23 via web (port 80)
Corp1(config)# access-list 100 permit tcp host 192.168.33.3 host 172.22.242.23 eq 80

Deny other hosts access to the Finance Web Server via web
Corp1(config)# access-list 100 deny tcp any host 172.22.242.23 eq 80

All other traffic is permitted
Corp1(config)# access-list 100 permit ip any any

Apply this access-list to Fa0/1 interface (outbound direction)
Corp1(config)# interface fa0/1
Corp1(config-if)# ip access-group 100 out

Finally, save the configuration
Corp1(config-if)# end
Corp1# copy running-config startup-config

Notice: We have to apply the access-list to Fa0/1 interface (not Fa0/0 interface) so that the access-list can filter traffic coming from both the LAN and the Core networks. If we apply access list to the inbound interface we can only filter traffic from the LAN network.

Click on host C to open its web browser. In the address box type http://172.22.242.23 to check if you are allowed to access Finance Web Server or not. If your configuration is correct then you can access it.

Click on other hosts (A, B and D) and check to make sure you can’t access Finance Web Server from these hosts.

CCNA – Access List Simulation 1

An administrator is trying to ping and telnet from SwitchC to RouterC with the results shown below.
CISCO CCNA Exam – Q336

Click the console connected to RouterC and issue the appropriate commands to answer the questions.
CISCO CCNA Exam – Q336b

For this question we only need to use the “show running-config” command to answer all the questions below

Router>enable
Router#show running-config

CISCO CCNA Exam – Q336c

CISCO CCNA Exam – Q336d

CISCO CCNA Exam – Q336e

Access List Simulation – Question 1

How can we fix the problem but only allow ping to work while disabling telnet?

A. Correctly assign an IP address to interface fa0/1
B. Change the ip access-group command on fa0/0 from “in” to “out”
C. Remove access-group 106 in from interface fa0/0 and add access-group 115 in.
D. Remove access-group 102 out from interface s0/0/0 and add access-group 114 in
E. Remove access-group 106 in from interface fa0/0 and add access-group 104 in

Answer: E

Explanation:

Let’s have a look at the access list 104:
CISCO CCNA Exam – Q336f

The question does not ask about ftp traffic so we don’t care about the two first lines. The 3rd line denies all telnet traffic and the 4th line allows icmp traffic to be sent (ping). Remember that the access list 104 is applied on the inbound direction so the 5th line “access-list 104 deny icmp any any echo-reply” will not affect our icmp traffic because the “echo-reply” message will be sent over the outbound direction.

Access List Simulation – Question 2
What will happen after issuing the command “ip access-group 114 in” to the fa0/0 interface?

A. Attempts to telnet to the router would fail
B. All traffic from the 10.4.4.0 network would be allow to go through
C. TCP and UDP traffic are not allowed to pass
D. Routing protocol updates for the 10.4.4.0 network would not be accepted from the fa0/0 interface

Answer: B

Explanation:
From the output of access-list 114: access-list 114 permit ip 10.4.4.0 0.0.0.255 any we can easily understand that this access list allows all traffic (ip) from 10.4.4.0/24 network.

Access List Simulation – Question 3

What will happen after issuing the command “access-group 115 in” on the s0/0/1 interface?

A. Hosts cannot connect to Router through s0/0/1
B. Telnet and ping would work but routing updates would fail.
C. FTP, FTP-DATA, echo, and HTTP traffic would work but telnet would fail
D. Only traffic from the 10.4.4.0 network would pass through the interface

Answer: A

Explanation:
First let’s see what was configured on interface S0/0/1:
CISCO CCNA Exam – Q336g

Recall that each interface only accepts one access-list, so when using the command “ip access-group 115 in” on the s0/0/1 interface it will overwrite the initial access-list 102. Therefore any telnet connection will be accepted (so we can eliminate answer C).
B is not correct because if telnet and ping can work then routing updates can, too.
D is not correct because access-list 115 does not mention about 10.4.4.0 network. So the most reasonable answer is A.

But here raise a question…

The wildcard mask of access-list 115, which is 255.255.255.0, means that only host with ip addresses in the form of x.x.x.0 will be accepted. But we all know that x.x.x.0 is likely to be a network address so the answer A: “no host could connect to Router through s0/0/1” seems right…

But what will happen if we don’t use a subnet mask of 255.255.255.0? For example we can use an ip address of 10.45.45.0 255.255.0.0, such a host with that ip address exists and we can connect to the router through that host. Now answer A seems incorrect!

CISCO CCNA Exam – Q335

A network administrator needs to configure a serial link between the main office and a remote location. The router at the remote office is a non-Cisco router. How should the network administrator configure the serial interface of the main office router to make the connection?

A.
Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# no shut
B.
Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# encapsulation ppp
Main(config-if)# no shut
C.
Main(config)# interface serial 0/0
Main(config-if)# ip address 172.16.1.1 255.255.255.252
Main(config-if)# encapsulation frame-relay
Main(config-if)# authentication chap
Main(config-if)# no shut
D.
Main(config)# interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#encapsulation ietf
Main(config-if)# no shut

Correct Answer: B

Explanation:
With serial point to point links there are two options for the encapsulation. The default, HDLC, is Cisco proprietary and works only with other Cisco routers. The other option is PPP which is standards based and supported by all vendors.

CISCO CCNA Exam – Q334

What are three reasons that an organization with multiple branch offices and roaming users might implement a Cisco VPN solution instead of point-to-point WAN links? (Choose three.)

A. reduced cost
B. better throughput
C. broadband incompatibility
D. increased security
E. scalability
F. reduced latency

Correct Answers: A, D, E

Explanation:
IPsec offer a number of advantages over point to point WAN links, particularly when multiple locations are involved. These include reduced cost, increased security since all traffic is encrypted, and increased scalability as a single WAN link can be used to connect to all locations in a VPN, where as a point to point link would need to be provisioned to each location.

CISCO CCNA Exam – Q333

Which two statistics appear in “show frame-relay map” output? (Choose two.)

A. the number of BECN packets that are received by the router
B. the value of the local DLCI
C. the number of FECN packets that are received by the router
D. the status of the PVC that is configured on the router
E. the IP address of the local router

Correct Answers: B,D

Explanation:
Sample “show frame-relay map” output:
R1#sh frame map
Serial0/0 (up): ip 10.4.4.1 dlci 401(0x191,0x6410), dynamic,
broadcast,, status defined, active
Serial0/0 (up): ip 10.4.4.3 dlci 403(0x193,0x6430), dynamic,
broadcast,, status defined, active
Serial0/0 (up): ip 10.4.4.4 dlci 401(0x191,0x6410), static,
CISCO, status defined, active

CISCO CCNA Exam – Q332

Users have been complaining that their Frame Relay connection to the corporate site is very slow. The network administrator suspects that the link is overloaded.
CISCO CCNA Exam – Q332

Based on the partial output of the Router# show frame relay pvc command shown in the graphic, which output value indicates to the local router that traffic sent to the corporate site is experiencing congestion?

A. DLCI = 100
B. last time PVC status changed 00:25:40
C. in BECN packets 192
D. in FECN packets 147
E. in DE packets 0

Correct Answer: C

Explanation:
If device A is sending data to device B across a Frame Relay infrastructure and one of the intermediate Frame Relay switches encounters congestion, congestion being full buffers, over-subscribed port, overloaded resources, etc, it will set the BECN bit on packets being returned to the sending device and the FECN bit on the packets being sent to the receiving device.

CISCO CCNA Exam – Q331

Which command allows you to verify the encapsulation type (CISCO or IETF) for a Frame Relay link?

A. show frame-relay lmi
B. show frame-relay map
C. show frame-relay pvc
D. show interfaces serial

Correct Answer: B

Explanation:
When connecting Cisco devices with non-Cisco devices, you must use IETF4 encapsulation on both devices. Check the encapsulation type on the Cisco device with the show frame-relay map exec command.

CISCO CCNA Exam – Q330

It has become necessary to configure an existing serial interface to accept a second Frame Relay virtual circuit. Which of the following procedures are required to accomplish this task? (Choose three.)

A. Remove the IP address from the physical interface.
B. Encapsulate the physical interface with multipoint PPP.
C. Create the virtual interfaces with the interface command.
D. Configure each subinterface with its own IP address.
E. Disable split horizon to prevent routing loops between the subinterface networks.
F. Configure static Frame Relay map entries for each subinterface network.

Correct Answers: A, C, D

Explanation:
For multiple PVC’s on a single interface, you must use subinterfaces, with each subinterface configured for each PVC. Each subinterface will then have its own IP address, and no IP address will be assigned to the main interface.

CISCO CCNA Exam – Q329

What occurs on a Frame Relay network when the CIR is exceeded?

A. All TCP traffic is marked discard eligible.
B. All UDP traffic is marked discard eligible and a BECN is sent.
C. All TCP traffic is marked discard eligible and a BECN is sent.
D. All traffic exceeding the CIR is marked discard eligible.

Correct Answer: D

Explanation:
Committed information rate (CIR): The minimum guaranteed data transfer rate agreed to by the Frame Relay switch. Frames that are sent in excess of the CIR are marked as discard eligible (DE) which means they can be dropped if the congestion occurs within the Frame Relay network.

Note: In the Frame Relay frame format, there is a bit called Discard eligible (DE) bit that is used to identify frames that are first to be dropped when the CIR is exceeded.