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Q1. Which flag in a configuration BPDU instructs all switches to shorten their bridge table aging process from the default 300 seconds to the current forward delay value?
A. topology change bit
B. topology change acknowledgment bit
C. priority bit
D. max-age bit
Answer: A
Explanation:
The Root Bridge continues to set the Topology Change flag (TCN bit) in all Configuration BPDUs that it sends out for a total of Forward Delay + Max Age seconds (default = 35 (20+15) seconds). This flag instructs all bridges to shorten their MAC address table (Bridge table) aging process from the default value of 300 seconds to the current Forward Delay value of the bridge (default=15 seconds). The TCA flag is set by the upstream bridge to tell the downstream bridges to stop sending TCN BPDUs. The TC flag is set in configuration BPDU by the Root Bridge to shorten the bridge table age-out period from default 300 seconds to Forward Delay seconds.
Q2. Which two options are mandatory components of a multiprotocol BGP VPN-IPv4 address? (Choose two.)
A. a route distinguisher
B. an IPv4 address
C. a route target
D. an MPLS label
E. a system ID
F. an area ID
Answer: A,B
Explanation:
The IP prefix is a member of the IPv4 address family. After the PE device learns the IP prefix, the PE converts it into a VPN-IPv4 prefix by combining it with an 8-byte route distinguisher (RD). The generated prefix is a member of the VPN-IPv4 address family. It uniquely identifies the customer address, even if the customer site is using globally nonunique (unregistered private) IP addresses. The route distinguisher used to generate the VPN-IPv4 prefix is specified by a configuration command associated with the virtual routing and forwarding (VRF) instance on the PE device.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l3_vpns/configuration/15-mt/mp-l3-vpns-15-mt-book/mp-bgp-mpls-vpn.html
Q3. Which two conditions must be met by default to implement the BGP multipath feature? (Choose two.)
A. The next-hop routers must be the same.
B. Route reflectors must be enabled.
C. All attributes must have the same values.
D. MPLS must be enabled.
E. The next-hop routers must be different.
Answer: C,E
Q4. 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.
Q5. How is the MRU for a multilink bundle determined?
A. It is negotiated by LCP.
B. It is manually configured on the multilink bundle.
C. It is manually configured on all physical interfaces of a multilink bundle.
D. It is negotiated by NCP.
E. It is negotiated by IPCP.
Answer: A
Q6. What does a nonzero forwarding address indicate in a type-5 LSA?
A. It indicates that this link-state ID is eligible for ECMP.
B. It indicates that this router should have an OSPF neighbor relationship with the forwarding address before using this link-state ID.
C. It indicates that the receiving router must check that the next hop is reachable in its routing table before using this link-state ID.
D. It indicates that traffic can be directly routed to this next hop in shared segment scenarios where the external route source is directly connected.
Answer: D
Explanation:
The value of the forwarding address specified by the autonomous system boundary router (ASBR) can be either 0.0.0.0 or non-zero. The 0.0.0.0 address indicates that the originating router (the ASBR) is the next hop. The forwarding address is determined by these conditions:
. The forwarding address is set to 0.0.0.0 if the ASBR redistributes routes and OSPF is not enabled on the next hop interface for those routes.
. These conditions set the forwarding address field to a non-zero address: ASBR's next hop interface address falls under the network range specified in the router ospf command.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13682-10.html
Q7. Refer to the exhibit.
Route exchange is failing on a PE edge device configured with this VRF-Lite. Which action can you take to correct the problem?
A. Configure the vrf-lite capability under the OSPF address families.
B. Correct the route descriptors.
C. Correct the OSPF router-ids.
D. Configure the control plane with a larger memory allocation to allow the device to appear in the routing table.
Answer: A
Explanation:
Open Shortest Path First version 3 (OSPFv3) operates in nondefault VPN routing and forwarding (VRF) instances for both IPv6 and IPv4 address families and, transports the routes across a Border Gateway Protocol (BGP) or a Multiprotocol Label Switching (MPLS) backbone. On the provider edge (PE) device, customer routes are installed together by OSPFv3 and BGP in a common VRF or address family and each protocol is configured to redistribute the routes of the other. BGP combines the prefixes redistributed into it with a route-distinguisher value defined for the VRF and advertises them to other MPLS-BGP speakers in the same autonomous system using the VPNv4 or VPNv6 address family as appropriate. The OSPFv3 route selection algorithm prefers intra-area routes across the back-door link over inter-area routes through the MPLS backbone. Sham-links are a type of virtual link across the MPLS backbone that connect OSPFv3 instances on different PEs. OSPFv3 instances tunnel protocol packets through the backbone and form adjacencies. Because OSPFv3 considers the sham-link as an intra-area connection, sham-link serves as a valid alternative to an intra-area back-door link. Domain IDs are used to determine whether the routes are internal or external. They describe the administrative domain of the OSPFv3 instance from which the route originates. Every PE has a 48-bit primary domain ID (which may be NULL) and zero or more secondary domain IDs.
How to Configure VRF-Lite/PE-CE
. Configuring a VRF in an IPv6 Address Family for OSPFv3
SUMMARY STEPS
1. enable
2. configure terminal
3. vrf definition vrf-name
4. rd route-distinguisher
5. exit
6. router ospfv3 [process-id]
7. address-family ipv6 [unicast] [vrf vrf-name]
8. end
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-sy/iro-15-sy-book/iro-vrf-lite-pe-ce.html
Q8. Refer to the exhibit.
What does the return code 3 represent in this output?
A. The mapping of the replying router for the FEC is different.
B. The packet is label-switched at stack depth.
C. The return code is reserved.
D. The upstream index is unknown.
E. The replying router was the proper egress for the FEC.
Answer: E
Explanation:
Return Codes The Return Code is set to zero by the sender. The receiver can set it to one of the values listed below. The notation <RSC> refers to the Return Subcode. This field is filled in with the stack-depth for those codes that specify that. For all other codes, the Return Subcode MUST be set to zero.
Value Meaning
0 No return code
1 Malformed echo request received
2 One or more of the TLVs was not understood
3 Replying router is an egress for the FEC at stack-depth <RSC>
4 Replying router has no mapping for the FEC at stack-depth <RSC>
Reference: https://www.ietf.org/rfc/rfc4379.txt
Q9. What is a key advantage of Cisco GET VPN over DMVPN?
A. Cisco GET VPN provides zero-touch deployment of IPSEC VPNs.
B. Cisco GET VPN supports certificate authentication for tunnel establishment.
C. Cisco GET VPN has a better anti-replay mechanism.
D. Cisco GET VPN does not require a secondary overlay routing infrastructure.
Answer: D
Explanation:
DMVPN requires overlaying a secondary routing infrastructure through the tunnels, which results in suboptimal routing while the dynamic tunnels are built. The overlay routing topology also reduces the inherent scalability of the underlying IP VPN network topology. Traditional point-to-point IPsec tunneling solutions suffer from multicast replication issues because multicast replication must be performed before tunnel encapsulation and encryption at the IPsec CE (customer edge) router closest to the multicast source. Multicast replication cannot be performed in the provider network because encapsulated multicasts appear to the core network as unicast data. Cisco’s Group Encrypted Transport VPN (GET VPN) introduces the concept of a trusted group to eliminate point-to-point tunnels and their associated overlay routing. All group members (GMs) share a common security association (SA), also known as a group SA. This enables GMs to decrypt traffic that was encrypted by any other GM. (Note that IPsec CE acts as a GM.) In GET VPN networks, there is no need to negotiate point-to- point IPsec tunnels between the members of a group, because GET VPN is “tunnel-less.”
Reference: Group Encrypted Transport VPN (Get VPN) Design and Implementation Guide PDF
Q10. Refer to the exhibit.
Which configuration reduces CPU utilization on R2 while still advertising the connected routes of R2 to R1?
A. Configure eigrp stub connected on R2.
B. Configure eigrp stub receive-only on R1.
C. Configure eigrp stub static on R2.
D. Configure eigrp stub summary on R1.
Answer: A