Download New Updated (July) Cisco 400-101 Actual Test 161-170

Ensurepass

 

QUESTION 161

Refer to the exhibit. Notice that debug ip bgp updates has been enabled. What can you conclude from the debug output?

 

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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.

 

Correct 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_PATHBGP(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

 

 

QUESTION 162

Which set of commands conditionally advertises 172.16.0.0/24 as long as 10.10.10.10/32 is in the routing table?

 

A.

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B.

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C.

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D.

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Correct Answer: B

Explanation:

Advertise maps are used for conditional routing to advertise specified prefixes if something which is specified in exist map exists. In our question we need to advertise 172.16.0.0/24 if 10.10.10.10/32 exists in the routing table so we have to use command. “neighbor x.x.x.x advertise-map <prefix-list of 172.16.0.0/24> exist-map <prefix-list of 10.10.10.10/32>”. Therefore B is correct.

 

 

QUESTION 163

Refer to the exhibit. Why is R2 unable to ping the loopback interface of R4?

 

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A.

The local preference is too high.

B.

The weight is too low.

C.

The next hop is not reachable from R2.

D.

The route originated from within the same AS.

 

Correct Answer: C

Explanation:

Before a BGP speaker installs a route to a network in the main IP routing table, the router must know how to reach the next hop that is used to get to that network. Route reachability is verified by searching for a route to the next hop in the main IP routing table. Unlike IGP routing protocols, such as EIGRP and OSPF, which assume that a route is reachable if they learned it through a valid adjacency, BGP does not install routes that it cannot verify as reachable. If a route to the next hop for a BGP network is found in the main IP routing table, BGP assumes that the network is reachable, and that the particular BGP route might be stored in the main IP routing table. If the router receives a route to a network that is not reachable, that route continues to be stored in the incoming BGP table, adj-RIB-In, and might be seen using the show ip bgp command, but is not placed in the main IP routing table.

Reference: https://www.informit.com/library/content.aspx?b=CCIE_Practical_Studies_II&seqNum=75

 

 

QUESTION 164

Which statement about the BGP originator ID is true?

 

A.

The route reflector always sets the originator ID to its own router ID.

B.

The route reflector sets the originator ID to the router ID of the route reflector client that injects the route into the AS.

C.

The route reflector client that injects the route into the AS sets the originator ID to its own router ID.

D.

The originator ID is set to match the cluster ID.

 

Correct Answer: B

Explanation:

An RR reflecting the route received from a RR-Client adds:

Reference: https://sites.google.com/site/amitsciscozone/home/bgp/bgp-route-reflectors

 

 

QUESTION 165

Refer to the exhibit. Which two statements are true? (Choose two.)

 

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A.

This router is not 4-byte autonomous system aware.

B.

This router is 4-byte autonomous system aware.

C.

The prefix 10.100.1.1/32 was learned through an autonomous system number with a length of 4 bytes, and this router is 4-byte autonomous system aware.

D.

The prefix 10.100.1.1/32 was learned through an autonomous system number with a length of 4 bytes, and this router is not 4-byte autonomous system aware.

E.

The prefix 10.100.1.1/32 was originated from a 4-byte autonomous system.

 

Correct Answer: AD

Explanation:

Prior to January 2009, BGP autonomous system (AS) numbers that were allocated to companies were 2-octet numbers in the range from 1 to 65535 as described in RFC 4271, A Border Gateway Protocol 4 (BGP-4). Due to increased demand for AS numbers, the Internet Assigned Number Authority (IANA) started to allocate four-octet AS numbers in the range from 65536 to 4294967295. RFC 5396, Textual Representation of Autonomous System (AS) Numbers, documents three methods of representing AS numbers. Cisco has implemented the following two methods:

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-4byte-asn.html

 

 

QUESTION 166

Refer to the exhibit. Which command is configured on this router?

 

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A.

bgp update-delay 60

B.

neighbor 10.100.1.1 maximum-prefix 200

C.

neighbor 10.100.1.1 maximum-path 2

D.

neighbor 10.100.1.1 ebgp-multihop 2

 

Correct Answer: B

Explanation:

The BGP Maximum-Prefix feature allows you to control how many prefixes can be received from a neighbor. By default, this feature allows a router to bring down a peer when the number of received prefixes from that peer exceeds the configured Maximum-Prefix limit. This feature is commonly used for external BGP peers, but can be applied to internal BGP peers also. When the maximum number of prefixes have been received, the BGP sessions closes into the IDLE state.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/25160-bgp-maximum-prefix.html

 

 

QUESTION 167

Refer to the exhibit. Why is network 172.16.1.0/24 not installed in the routing table?

 

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A.

There is no ARP entry for 192.168.1.1.

B.

The router cannot ping 192.168.1.1.

C.

The neighbor 192.168.1.1 just timed out and BGP will flush this prefix the next time that the BGP scanner runs.

D.

There is no route for 192.168.1.1 in the routing table.

 

Correct Answer: D

Explanation:

Here we see that the next hop IP address to reach the 172.16.1.0 network advertised by the BGP peer is 192.168.1.1. However, the 192.168.1.1 IP is not in the routing table of R3 so it adds the route to the BGP table but marks it as inaccessible, as shown.

 

 

QUESTION 168

Refer to the exhibit. Which two statements are true? (Cho
ose two.)

 

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A.

This is the output of the show ip ospf command.

B.

This is the output of the show ip protocols command.

C.

This router is an ABR.

D.

This router is an ASBR.

E.

Authentication is not configured for the area.

Correct Answer: AE

Explanation:

The following is sample output from the show ip ospf command when entered without a specific OSPF process ID with no authentication

Router# show ip ospf

 

Routing Process “ospf 201” with ID 10.0.0.1 and Domain ID 10.20.0.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

SPF schedule delay 5 secs, Hold time between two SPFs 10 secs

Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs

LSA group pacing timer 100 secs

Interface flood pacing timer 55 msecs

Retransmission pacing timer 100 msecs

Number of external LSA 0. Checksum Sum 0x0

Number of opaque AS LSA 0. Checksum Sum 0x0

Number of DCbitless external and opaque AS LSA 0

Number of DoNotAge external and opaque AS LSA 0

Number of areas in this router is 2. 2 normal 0 stub 0 nssa

External flood list length 0

Area BACKBONE(0)

Number of interfaces in this area is 2

Area has no authentication

SPF algorithm executed 4 times

Area ranges are

Number of LSA 4. Checksum Sum 0x29BEB

Number of opaque link LSA 0. Checksum Sum 0x0

Number of DCbitless LSA 3

Number of indication LSA 0

Number of DoNotAge LSA 0

Flood list length 0

 

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/command/iro-cr-book/ospf-s1.html#wp8749965360

 

 

QUESTION 169

Consider a network that mixes link bandwidths from 128 kb/s to 40 Gb/s. Which value should be set for the OSPF reference bandwidth?

 

A.

Set a value of 128.

B.

Set a value of 40000.

C.

Set a manual OSPF cost on each interface.

D.

Use the default value.

E.

Set a value of 40000000.

F.

Set a value of 65535.

 

Correct Answer: C

Explanation:

Unlike the metric in RIP which is determined by hop count and EIGRP’s crazy mathematical formulated metric, OSPF is a little more simple. The default formula to calculate the cost for the OSPF metric is (10^8/BW).

By default the metrics reference cost is 100Mbps, so any link that is 100Mbps will have a metric of  a T1 interface will have a metric of 64 so in this case if a router is trying to get to a FastEthernet network on a router that is through a T1 the metric would be 65 (64 +1).

You do however have the ability to statically specify a metric on a per interface basis by using the ip ospf cost # where the cost is an integer between 1-65535.

So the big question is why would you want to statically configure a metric?

The biggest advantage of statically configuring an OSPF metric on an interface is to manipulate which route will be chosen dynamically via OSPF. In a nut shell it’s like statically configuring a dynamic protocol to use a specific route. It should also be used when the interface bandwidths vary greatly (some very low bandwidth interfaces and some very high speed interfaces on the same router).

 

 

QUESTION 170

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.

 

Correct 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.

 

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