[2021-New] Cisco 400-101 Dumps With Update Exam Questions (51-60)

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Q1. Refer to the exhibit.

Notice that debug ip bgp updates have been enabled. What can you conclude from the debug output?

A. This is the result of the clear ip bgp 10.1.3.4 in command.

B. This is the result of the clear ip bgp 10.1.3.4 out command.

C. BGP neighbor 10.1.3.4 performed a graceful restart.

D. BGP neighbor 10.1.3.4 established a new BGP session.

Answer: A

Explanation:

If you enter the clear ip bgp out command for a BGP peer, that router resends its BGP prefixes to that peer. This does not cause a change in the best path on the receiving BGP peer. Hence, there is no change in the Table Version on that peer.

When you run the debug ip bgp updates on the receiving router, you see:

BGP(0): 10.1.3.4 rcvd UPDATE w/ attr: nexthop 10.1.3.4, origin i, metric 0, merged path 4, AS_PATH

BGP(0): 10.1.3.4 rcvd 10.100.1.1/32...duplicate ignored

The received update is recognized as a duplicate, so it is ignored and no best path change occurs.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/116511-technote-tableversion-00.html

Q2. Which map is locally defined?

A. DSCP-to-DSCP-mutation

B. CoS-to-DSCP

C. IP-precedence-to-DSCP

D. DSCP-to-CoS

Answer: A

Q3. Which multicast protocol uses source trees and RPF?

A. DVMRP

B. PIM sparse mode

C. CBT

D. mOSPF

Answer: A

Explanation:

DVMRP builds a parent-child database using a constrained multicast model to build a forwarding tree rooted at the source of the multicast packets. Multicast packets are initially flooded down this source tree. If redundant paths are on the source tree, packets are not forwarded along those paths. Forwarding occurs until prune messages are received on those parent-child links, which further constrains the broadcast of multicast packets.

Reference: DVMRP and dense-mode PIM use only source trees and use RPF as previously described.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_19_ea1/configuration/guide/3550scg/swmcast.html

Q4. Refer to the exhibit.

Router R2 is learning the 192.168.1.0/24 network from R1 via EIGRP and eBGP. R2 then redistributes EIGRP into OSPF as metric-type 2 with default metrics. Which metric of the route in the R3 routing table?

A. 20

B. 30

C. 110

D. The route is not present in the R3 routing table.

Answer: D

Q5. Refer to the exhibit.

Which two actions can you take to enable CE-1 at site A to access the Internet? (Choose two.)

A. Create a default route for site A on PE-1 with the next hop set to the PE-2 interface to the Internet.

B. Originate a default route in site B with the next hop set to the PE-2 Internet interface, and import the default route into site A.

C. Create a default route on CE-1 with the next hop set to the PE-1 upstream interface.

D. Originate a default route in site A with the next hop set to the PE-2 interface to CE-1.

E. Create a static default route on CE-1 with the next hop set to the PE-2 interface to the Internet.

Answer: A,B

Q6. Which two statements about packet fragmentation on an IPv6 network are true? (Choose two.)

A. The fragment header is 64 bits long.

B. The identification field is 32 bits long.

C. The fragment header is 32 bits long.

D. The identification field is 64 bits long.

E. The MTU must be a minimum of 1280 bytes.

F. The fragment header is 48 bits long.

Answer: A,B

Explanation:

The fragment header is shown below, being 64 bits total with a 32 bit identification field:

Reference: http://www.openwall.com/presentations/IPv6/img24.html

Q7. Which two statements about BGP prefix-based outbound filtering are true? (Choose two.)

A. It must be configured per address family.

B. It can use prefix lists and route maps for filtering.

C. It can be configured under the global BGP routing process.

D. It can be configured for external peering sessions only.

E. It can increase the processing load on the router.

F. It supports IP multicast routes.

Answer: A,D

Q8. DRAG DROP

Drag each statement about EtherChannel protocols on the left to the matching EtherChannel protocol on the right.

Answer:

Q9. When you configure the ip pmtu command under an L2TPv3 pseudowire class, which two things can happen when a packet exceeds the L2TP path MTU? (Choose two.)

A. The router drops the packet.

B. The router always fragments the packet after L2TP/IP encapsulation.

C. The router drops the packet and sends an ICMP unreachable message back to the sender only if the DF bit is set to 1.

D. The router always fragments the packet before L2TP/IP encapsulation.

E. The router fragments the packet after L2TP/IP encapsulation only if the DF bit is set to 0.

F. The router fragments the packet before L2TP/IP encapsulation only if the DF bit is set to

Answer: C,F

Explanation:

If you enable the ip pmtu command in the pseudowire class, the L2TPv3 control channel participates in the path MTU discovery. When you enable this feature, the following processing is performed:

– ICMP unreachable messages sent back to the L2TPv3 router are deciphered and the tunnel MTU is updated accordingly. In order to receive ICMP unreachable messages for fragmentation errors, the DF bit in the tunnel header is set according to the DF bit value received from the CE, or statically if the ip dfbit set option is enabled. The tunnel MTU is periodically reset to the default value based on a periodic timer.

– ICMP unreachable messages are sent back to the clients on the CE side. ICMP unreachable messages are sent to the CE whenever IP packets arrive on the CE-PE interface and have a packet size greater than the tunnel MTU. A Layer 2 header calculationis performed before the ICMP unreachable message is sent to the CE.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/l2tpv325.html

Q10. Refer to the exhibit.

All switches have default bridge priorities, and originate BPDUs with MAC addresses as indicated. The numbers shown are STP link metrics. Which two ports are forwarding traffic after STP converges? (Choose two.)

A. The port connecting switch SWD with switch SWE

B. The port connecting switch SWG with switch SWF

C. The port connecting switch SWC with switch SWE

D. The port connecting switch SWB with switch SWC

Answer: C,D

Explanation:

Here, we know SWB to SWC are forwarding because we already identified the blocking port. So for the last correct answer let’s consider what must be done to prevent a switch loop between SWC/SWD/SWE. SWE to SWD will be blocked because SWC has a lower MAC address so it wins the forwarding port. And to look at it further, you could try to further understand what would happen with ports on SWG. Would the ports on SWG try to go through SWE or SWF? SWE has the lower MAC address so the port from SWG to SWE would win the forwarding election. Therefore, answer B could never be correct.