CISCO CCNA Exam – Q253

Which encapsulation type is a Frame Relay encapsulation type that is supported by Cisco routers?

A. IETF
B. ANSI Annex D
C. Q9333-A Annex A
D. HDLC

Correct Answer: A

Explanation:
Cisco supports two Frame Relay encapsulation types: the Cisco encapsulation and the IETF Frame Relay encapsulation, which is in conformance with RFC 1490 and RFC 2427. The former is often used to connect two Cisco routers while the latter is used to connect a Cisco router to a non-Cisco router. You can test with your Cisco router when typing the command Router(config-if)#encapsulation frame-relay ? on a WAN link. Below is the output of this command (notice Cisco is the default encapsulation so it is not listed here, just press Enter to use it).
CISCO CCNA Exam – Q253

HDLC is a WAN protocol same as Frame-Relay and PPP so it is not a Frame Relay encapsulation type.

CISCO CCNA Exam – Q252

RouterA is unable to reach RouterB. Both routers are running IOS version 12.0.
CISCO CCNA Exam – Q252

After reviewing the command output and graphic, what is the most likely cause of the problem?

A. incorrect bandwidth configuration
B. incorrect LMI configuration
C. incorrect map statement
D. incorrect IP address

Correct Answer: C

Explanation:
First we have to say this is an unclear question and it is wrong. The “frame-relay map ip” statement is correct thus none of the four answers above is correct. But we guess there is a typo in the output. Maybe the “ip address 172.16.100.2 255.255.0.0″ command should be “ip address 172.16.100.1 255.255.0.0″. That makes answer C correct.

CISCO CCNA Exam – Q251

Refer to the exhibit.
CISCO CCNA Exam – Q251

What is the meaning of the term dynamic as displayed in the output of the show frame-relay map command shown?

A. The Serial0/0 interface is passing traffic.
B. The DLCI 100 was dynamically allocated by the router.
C. The Serial0/0 interface acquired the IP address of 172.16.3.1 from a DHCP server.
D. The DLCI 100 will be dynamically changed as required to adapt to changes in the Frame Relay cloud.
E. The mapping between DLCI 100 and the end station IP address 172.16.3.1 was learned through Inverse ARP.

Correct Answer: E

Explanation:
Inverse Address Resolution Protocol (Inverse ARP) was developed to provide a mechanism for dynamic DLCI to Layer 3 address maps. Inverse ARP works much the same way Address Resolution Protocol (ARP) works on a LAN. However, with ARP, the device knows the Layer 3 IP address and needs to know the remote data link MAC address. With Inverse ARP, the router knows the Layer 2 address which is the DLCI, but needs to know the remote Layer 3 IP address.

When using dynamic address mapping, Inverse ARP requests a next-hop protocol address for each active PVC. Once the requesting router receives an Inverse ARP response, it updates its DLCI-to-Layer 3 address mapping table. Dynamic address mapping is enabled by default for all protocols enabled on a physical interface. If the Frame Relay environment supports LMI autosensing and Inverse ARP, dynamic address mapping takes place automatically. Therefore, no static address mapping is required.

CISCO CCNA Exam – Q250

Which statement describes the process ID that is used to run OSPF on a router?

A. It is globally significant and is used to represent the AS number.
B. It is locally significant and is used to identify an instance of the OSPF database.
C. It is globally significant and is used to identify OSPF stub areas.
D. It is locally significant and must be the same throughout an area.

Correct Answer: B

Explanation:
The Process ID for OSPF on a router is only locally significant and you can use the same number on each router, or each router can have a different number-it just doesn’t matter. The numbers you can use are from 1 to 65,535. Don’t get this confused with area numbers, which can be from 0 to 4.2 billion.

CISCO CCNA Exam – Q249

Which statement is correct regarding the operation of DHCP?

A. A DHCP client uses a ping to detect address conflicts.
B. A DHCP server uses a gratuitous ARP to detect DHCP clients.
C. A DHCP client uses a gratuitous ARP to detect a DHCP server.
D. If an address conflict is detected, the address is removed from the pool and an administrator must resolve the conflict.
E. If an address conflict is detected, the address is removed from the pool for an amount of time configurable by the administrator.
F. If an address conflict is detected, the address is removed from the pool and will not be reused until the server is rebooted.

Correct Answer: D

Explanation:
An address conflict occurs when two hosts use the same IP address. During address assignment, DHCP checks for conflicts using ping and gratuitous ARP. If a conflict is detected, the address is removed from the pool. The address will not be assigned until the administrator resolves the conflict.

CISCO CCNA Exam – Q248

Refer to the exhibit.
CISCO CCNA Exam – Q248

What statement is true of the configuration for this network?

A. The configuration that is shown provides inadequate outside address space for translation of the number of inside addresses that are supported.
B. Because of the addressing on interface FastEthernet0/1, the Serial0/0 interface address will not support the NAT configuration as shown.
C. The number 1 referred to in the ip nat inside source command references access-list number 1.
D. ExternalRouter must be configured with static routes to networks 172.16.1.0/24 and 172.16.2.0/24.

Correct Answer: C

Explanation:
The “list 1″ refers to the access-list number 1.

CISCO CCNA Exam – Q247

Which statement describes the process of dynamically assigning IP addresses by the DHCP server?

A. Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement.
B. Addresses are permanently assigned so that the hosts uses the same address at all times.
C. Addresses are assigned for a fixed period of time, at the end of the period, a new request for an address must be made.
D. Addresses are leased to hosts, which periodically contact the DHCP server to renew the lease.

Correct Answer: D

Explanation:
The DHCP lifecycle consists of the following:
Allocation: A client begins with no active lease, and hence, no DHCP-assigned address. It acquires a lease through a process of allocation.

Reallocation: If a client already has an address from an existing lease, then when it reboots or starts up after being shut down, it will contact the DHCP server that granted it the lease to confirm the lease and acquire operating parameters. This is sometimes called reallocation; it is similar to the full allocation process but shorter.

Normal Operation: Once a lease is active, the client functions normally, using its assigned IP address and other parameters during the “main part” of the lease. The client is said to be bound to the lease and the address.

Renewal: After a certain portion of the lease time has expired, the client will attempt to contact the server that initially granted the lease, to renew the lease so it can keep using its IP address.

Rebinding. If renewal with the original leasing server fails (because, for example, the server has been taken offline), then the client will try to rebind to any active DHCP server, trying to extend its current lease with any server that will allow it to do so.

Release: The client may decide at any time that it no longer wishes to use the IP address it was assigned, and may terminate the lease, releasing the IP address.

CISCO CCNA Exam – Q246

What are two benefits of using NAT? (Choose two.)

A. NAT facilitates end-to-end communication when IPsec is enabled.
B. NAT eliminates the need to re-address all hosts that require external access.
C. NAT conserves addresses through host MAC-level multiplexing.
D. Dynamic NAT facilitates connections from the outside of the network.
E. NAT accelerates the routing process because no modifications are made on the packets.
F. NAT protects network security because private networks are not advertised.

Correct Answers: B, F

Explanation:
By not revealing the internal IP addresses, NAT adds some security to the inside network -> F is correct.
NAT has to modify the source IP addresses in the packets -> E is not correct.
Connection from the outside of the network through a “NAT” network is more difficult than a more network because IP addresses of inside hosts are hidden -> C is not correct.
In order for IPsec to work with NAT we need to allow additional protocols, including Internet Key Exchange (IKE), Encapsulating Security Payload (ESP) and Authentication Header (AH) -> more complex -> A is not correct.
By allocating specific public IP addresses to inside hosts, NAT eliminates the need to re-address the inside hosts -> B is correct.
NAT does conserve addresses but not through host MAC-level multiplexing. It conserves addresses by allowing many private IP addresses to use the same public IP address to go to the Internet -> C is not correct.

CISCO CCNA Exam – Q245

On which options are standard access lists based?

A. destination address and wildcard mask
B. destination address and subnet mask
C. source address and subnet mask
D. source address and wildcard mask

Correct Answer: D

Explanation:
Standard ACL’s only examine the source IP address/mask to determine if a match is made. Extended ACL’s examine the source and destination address, as well as port information.

CISCO CCNA Exam – Q244

A network engineer wants to allow a temporary entry for a remote user with a specific username and password so that the user can access the entire network over the Internet. Which ACL can be used?

A. standard
B. extended
C. dynamic
D. reflexive

Correct Answer: C

Explanation:
We can use a dynamic access list to authenticate a remote user with a specific username and password. The authentication process is done by the router or a central access server such as a TACACS+ or RADIUS server. The configuration of dynamic ACL can be read here: http://www.cisco.com/en/US/tech/tk583/tk822/technologies_tech_note09186a0080094524.shtml