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Q401. Refer to the exhibit. 

Which action must you take to enable the WAN link to function properly? 

A. Enter a clock rate on the DCE interface. 

B. Enter a clock rate on the DTE interface. 

C. Enter a compression algorithm on both interfaces. 

D. Configure both interfaces for HDLC encapsulation. 

Answer: A 

Explanation: 

When connecting a serial cable to the serial interface of the router, clocking is provided by an external device, such as a CSU/DSU device. A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a router to a digital circuit. The router is the DTE (Data Terminal Equipment) and the external device is the DCE (Data Communications Equipment), where the DCE provides the clocking. However, in some cases we might connect two routers back-to-back using the routers’ serial interfaces (Example. Inside the router labs). Each router is a DTE by default. Since clocking is required to enable the interface, one of the two routers should function as DCE and should provide clocking. This can be done by using the "clock rate" command, from the interface configuration mode. 

Reference: http://www.omnisecu.com/cisco-certified-network-associate-ccna/how-to-configure-router-serial-interfaces.php 


Q402. A company is multihomed to several Internet providers using EBGP. Which two measures guarantee that the network of the company does not become a transit AS for Internet traffic? (Choose two.) 

A. Prepend three times the AS number of the company to the AS path list. 

B. Add the community NO_EXPORT when sending updates to EBGP neighbors. 

C. Write AS-path access-list which permits one AS long paths only and use it to filter updates sent to EBGP neighbors. 

D. Add the community NO_EXPORT when receiving updates from EBGP neighbors. 

Answer: C,D 

Explanation: 

By default BGP will advertise all prefixes to EBGP (External BGP) neighbors. This means that if you are multi-homed (connected to two or more ISPs) that you might become a transit AS. Let me show you an example: 

R1 is connected to ISP1 and ISP2 and each router is in a different AS (Autonomous System). Since R1 is multi-homed it’s possible that the ISPs will use R1 to reach each other. In order to prevent this we’ll have to ensure that R1 only advertises prefixes from its own autonomous system. As far as I know there are 4 methods how you can prevent becoming a transit AS: 

Filter-list with AS PATH access-list. 

No-Export Community. 

Prefix-list Filtering 

Distribute-list Filtering 

Reference: http://networklessons.com/bgp/bgp-prevent-transit-as/ 


Q403. Refer to the exhibit. 

Why is the router out of memory? 

A. The router is experiencing a BGP memory leak software defect. 

B. The BGP peers have been up for too long. 

C. The amount of BGP update traffic in the network is too high. 

D. The router has insufficient memory due to the size of the BGP database. 

Answer: D 

Explanation: 

Here we can see that this router is running out of memory due to the large size of the BGP routing database. In this case, this router is receiving over 200,000 routes from each of the 4 peers. 


Q404. Refer to the exhibit. 

Which statement is true? 

A. There is an MPLS network that is running 6PE, and the ingress PE router has no mpls ip propagate-ttl. 

B. There is an MPLS network that is running 6VPE, and the ingress PE router has no mpls ip propagate-ttl. 

C. There is an MPLS network that is running 6PE or 6VPE, and the ingress PE router has mpls ip propagate-ttl. 

D. There is an MPLS network that is running 6PE, and the ingress PE router has mpls ip propagate-ttl. 

E. There is an MPLS network that is running 6VPE, and the ingress PE router has mpls ip propagate-ttl. 

Answer: C 

Explanation: 

The second hop shows and IPV6 address over MPLS, so we know that there is an MPLS network running 6PE or 6VPE. And because the second and third hops show up in the traceroute. Then TTL is being propagated because if the “no ip propagate-ttl” command was used these devices would be hidden in the traceroute. 


Q405. What are the three modes of Unicast Reverse Path Forwarding? 

A. strict mode, loose mode, and VRF mode 

B. strict mode, loose mode, and broadcast mode 

C. strict mode, broadcast mode, and VRF mode 

D. broadcast mode, loose mode, and VRF mode 

Answer: A 


Q406. Which three statements are true about PPP CHAP authentication? (Choose three.) 

A. PPP encapsulation must be enabled globally. 

B. The LCP phase must be complete and in closed state. 

C. The hostname used by a router for CHAP authentication cannot be changed. 

D. PPP encapsulation must be enabled on the interface. 

E. The LCP phase must be complete and in open state. 

F. By default, the router uses its hostname to identify itself to the peer. 

Answer: D,E,F 

Explanation: 

Point-to-Point Protocol (PPP) authentication issues are one of the most common causes for dialup link failures. This document provides some troubleshooting procedures for PPP authentication issues. 

Prerequisites 

. Enable PPP encapsulation 

. The PPP authentication phase does not begin until the Link Control Protocol (LCP) phase is complete and is in the open state. If debug ppp negotiation does not indicate that LCP is open, troubleshoot this issue before proceeding. 

Note. By default, the router uses its hostname to identify itself to the peer. However, this CHAP username can be changed through the ppp chap hostname command. 

Reference: http://www.cisco.com/c/en/us/support/docs/wan/point-to-point-protocol-ppp/25647-understanding-ppp-chap.html 


Q407. Which two options are contained in the MSG part of a syslog message? (Choose two.) 

A. TAG field 

B. CONTENT field 

C. three-digit priority value 

D. IP address of the sending device 

E. TLS port number 

Answer: A,B 


Q408. Refer to the exhibit. 

Which statement about this device configuration is true? 

A. The NMS needs a specific route configured to enable it to reach the Loopback0 interface of the device. 

B. The ifindex of the device could be different when the device is reloaded. 

C. The device will allow anyone to poll it via the public community. 

D. The device configuration requires the AuthNoPriv security level. 

Answer: B 

Explanation: 

One of the most commonly used identifiers in SNMP-based network management applications is the Interface Index (ifIndex) value. IfIndex is a unique identifying number associated with a physical or logical interface. For most software, the ifIndex is the name of the interface. Although relevant RFCs do not require that the correspondence between particular ifIndex values and their interfaces be maintained across reboots, applications such as device inventory, billing, and fault detection depend on this correspondence. Consider a situation where a simple monitoring software (like MRTG) is polling the interface statistics of the router specific serial interface going to the internet. 

As an example, you could have these conditions prior to re-initialization: 

physical port ifIndex 

ethernet port 

tokenring port 

2 

serial port 

3 

Therefore, the management application is polling the ifIndex 3, which corresponds to the serial port. 

After the router re-initialization (reboot, reload and so on) the conditions change to something similar to this: 

physical port 

ifIndex 

ethernet port 

3 

tokenring port 

1 

serial port 

2 

The management application continues polling the ifIndex 3, which corresponds now to the ethernet port. Therefore, if the management application is not warned by a trap, for example, that the router has been rebooted, the statistics polled could be completely wrong. 

Reference: http://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol-snmp/28420-ifIndex-Persistence.html 


Q409. Refer to the exhibit. 

Why is the loopback 0 interface of R4 missing in the routing table of R2? 

A. R2 is configured as a route reflector client. 

B. There is no peering between R2 and R3. 

C. The next hop is not reachable from R2. 

D. The route originated within the same AS. 

Answer: B 

Explanation: 

In the “show ip bgp” output we see that there is no peering session between R2 and R3. Since R3 is the route reflector here, R3 would reflect routes advertised from R4 to R2, but the peer needs to be established first. 


Q410. Which two statements about redistribution are true? (Choose two.) 

A. EIGRP requires the route to have a default metric defined. 

B. EIGRP and OSPF use their router IDs to prevent loops. 

C. When OSPF is redistributed into IS-IS, the default metric must be configured under the IS-IS process. 

D. When traffic is redistributed into OSPF, the subnets command is needed to redistribute classful subnets. 

E. The default seed metric for OSPF redistributed routes is 30. 

Answer: A,B