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Q311. Which problem can result when private AS numbers are included in advertisements that are sent to the global Internet BGP table?
A. The prefixes sent with private AS numbers are always discarded on the Internet.
B. The prefixes sent with private AS numbers are always tagged as invalid on the Internet.
C. The prefixes sent with private AS numbers lack uniqueness, which can lead to a loss of connectivity.
D. The prefixes sent with private AS numbers are sometimes tagged as invalid on the Internet.
Answer: C
Explanation:
Private AS numbers are not meant to be used for global Internet BGP routing, as they are assigned locally and can be used by any organization. They are meant to enable BGP within a enterprise or VPN, but since these numbers can be used by any organization they are not unique and could cause connectivity loss if leaked to the Internet.
Q312. With which ISs will an IS-IS Level 1 IS exchange routing information?
A. Level 1 ISs
B. Level 1 ISs in the same area
C. Level 1 and Level 2 ISs
D. Level 2 ISs
Answer: B
Explanation:
IS-IS differs from OSPF in the way that "areas" are defined and routed between. IS-IS routers are designated as being: Level 1 (intra-area); Level 2 (inter area); or Level 1-2 (both). Level 2 routers are inter area routers that can only form relationships with other Level 2 routers. Routing information is exchanged between Level 1 routers and other Level 1 routers, and Level 2 routers only exchange information with other Level 2 routers. Level 1-2 routers exchange information with both levels and are used to connect the inter area routers with the intra area routers.
Reference: http://en.wikipedia.org/wiki/IS-IS
Q313. Refer to the exhibit.
Which BGP feature allows R1 to instruct R2 which prefixes it is allowed to advertise to R1?
A. route refresh
B. Prefix-Based Outbound Route Filtering
C. distribute lists
D. prefix lists
Answer: B
Q314. EIGRP allows configuration of multiple MD5 keys for packet authentication to support easy rollover from an old key to a new key. Which two statements are true regarding the usage of multiple authentication keys? (Choose two.)
A. Received packets are authenticated by the key with the smallest key ID.
B. Sent packets are authenticated by all valid keys, which means that each packet is replicated as many times as the number of existing valid keys.
C. Received packets are authenticated by any valid key that is chosen.
D. Sent packets are authenticated by the key with the smallest key ID.
Answer: C,D
Explanation:
Suppose two routers are connected with each other via Fa0/0 interfaces and they are configured to authenticate via MD5. Below is a simple configuration on both routers so that they will work:
Router1(config)#key chain KeyChainR1
Router1(config-keychain)#key 1
Router1(config-keychain-key)#key-string FirstKey
Router1(config-keychain-key)#key 2
Router1(config-keychain-key)#key-string SecondKey
Router2(config)#key chain KeyChainR2
Router2(config-keychain)#key 1
Router2(config-keychain-key)#key-string FirstKey
Router2(config-keychain-key)#key 2
Router2(config-keychain-key)#key-string SecondKey
Apply these key chains to R1 & R2:
Router1(config)#interface fastEthernet 0/0
Router1(config-if)#ip authentication mode eigrp 1 md5
Router1(config-if)#ip authentication key-chain eigrp 1 KeyChainR1
Router2(config)#interface fastEthernet 0/0
Router2(config-if)#ip authentication mode eigrp 1 md5
Router2(config-if)#ip authentication key-chain eigrp 1 KeyChainR2
There are some rules to configure MD5 authentication with EIGRP:
+ The key chain names on two routers do not have to match (in this case the name “KeyChainR1 & “KeyChainR2 do not match)
+ The key number and key-string on the two potential neighbors must match (for example “key 1 & “key-string FirstKey” must match on “key 1” & “key-string FirstKey” of neighboring router) Also some facts about MD5 authentication with EIGRP
+ When sending EIGRP messages the lowest valid key number is used -> D is correct.
+ When receving EIGRP messages all currently configured valid keys are verified but the lowest valid one will be used -> Although answer C does not totally mention like that but it is the most suitable answer because A and B are totally wrong. Answer A is not correct because we need valid key to authenticate. As mentioned above, although answer C is not totally correct but it puts some light on why
answer B is not correct: each packet is NOT “replicated as many times as the number of existing valid keys”. All currently configured valid keys are verified but the lowest valid one will be used.
Q315. Which two statements about reverse ARP are true? (Choose two.)
A. Its servers require static mappings.
B. It works with AutoInstall to configure new devices.
C. It provides IP addresses for subnet masks.
D. It provides IP addresses for default gateways.
E. It requires less maintenance than DHCP.
Answer: A,B
Q316. Refer to the exhibit.
Which two benefits result from using this command on a switch? (Choose two.)
A. The port cannot forward unknown unicast packets.
B. Network security is increased on the configured port.
C. The port cannot forward unknown multicast packets.
D. The port cannot forward unknown broadcast packets.
E. Network security is increased on all ports of the switch.
F. Unknown packets of all types, except unicast, are blocked.
Answer: A,B
Q317. Which statement about a type 4 LSA in OSPF is true?
A. It is an LSA that is originated by an ABR, that is flooded throughout the AS, and that describes a route to the ASBR.
B. It is an LSA that is originated by an ASBR, that is flooded throughout the AS, and that describes a route to the ASBR.
C. It is an LSA that is originated by an ASBR, that is flooded throughout the area, and that describes a route to the ASBR.
D. It is an LSA that is originated by an ABR, that is flooded throughout the AS, and that describes a route to the ABR.
E. It is an LSA that is originated by an ABR, that is flooded throughout the area, and that describes a route to the ASBR.
Answer: E
Explanation:
LSA Type 4 (called Summary ASBR LSA) is generated by the ABR to describe an ASBR to routers in other areas so that routers in other areas know how to get to external routes through that ASBR.
Q318. An IP SLA fails to generate statistics. How can you fix the problem?
A. Add the verify-data command to the router configuration.
B. Reload the router configuration.
C. Remove the ip sla schedule statement from the router configuration and re-enter it.
D. Add the debug ip sla error command to the router configuration.
E. Add the debug ip sla trace command to the router configuration.
Answer: A
Q319. Refer to the exhibit.
Service provider SP 1 is running the MPLS-VPN service. The MPLS core network has MP-BGP configured with RR-1 as route reflector. What will be the effect on traffic between PE1 and PE2 if router P1 goes down?
A. No effect, because all traffic between PE1 and PE2 will be rerouted through P2.
B. No effect, because P1 was not the only P router in the forwarding path of traffic.
C. No effect, because RR-1 will find an alternative path for MP-BGP sessions to PE-1 and PE-2.
D. All traffic will be lost because RR-1 will lose the MP-BGP sessions to PE-1 and PE-2.
Answer: D
Explanation:
If the connection to the route reflector goes down, then routes from PE-1 will not get advertised to PE2, and vice versa. Route reflectors are critical in an MPLS VPN such as the one shown, which is why it is a best practice to have multiple route reflectors in this kind of network.
Q320. Which topology allows the split-horizon rule to be safely disabled when using EIGRP?
A. full mesh
B. partial mesh
C. hub and spoke
D. ring
Answer: C