[2021-New] Cisco 400-101 Dumps With Update Exam Questions (131-140)

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Q1. Which two methods can you use to limit the range for EIGRP queries? (Choose two.)

A. Use an access list to deny the multicast address 224.0.0.1 outbound from select EIGRP neighbor and permit everything else.

B. Configure route tagging for all EIGRP routes.

C. Summarize routes at the boundary routers of the EIGRP domain.

D. Configure unicast EIGRP on all routers in the EIGRP domain.

E. Configure stub routers in the EIGRP domain.

F. Use an access list to deny the multicast address 224.0.0.10 outbound from select EIGRP neighbors and permit everything else.

Answer: C,E

Q2. Refer to the exhibit.

Which statement is true?

A. 2001:DB8::1/128 is a local host route, and it can be redistributed into a dynamic routing protocol.

B. 2001:DB8::1/128 is a local host route, and it cannot be redistributed into a dynamic routing protocol.

C. 2001:DB8::1/128 is a local host route that was created because ipv6 unicast-routing is not enabled on this router.

D. 2001:DB8::1/128 is a route that was put in the IPv6 routing table because one of this router's loopback interfaces has the IPv6 address 2001:DB8::1/128.

Answer: B

Explanation:

The local routes have the administrative distance of 0. This is the same adminstrative distance as connected routes. However, when you configure redistributed connected under any routing process, the connected routes are redistributed, but the local routes are not. This behavior allows the networks to not require a large number of host routes, because the networks of the interfaces are advertised with their proper masks. These host routes are only needed on the router that owns the IP address in order to process packets destined to that IP address.

It is normal for local host routes to be listed in the IPv4 and IPv6 routing table for IP addresses of the router's interfaces. Their purpose is to create a corresponding CEF entry as a receive entry so that the packets destined to this IP address can be processed by the router itself. These routes cannot be redistributed into any routing protocol.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/ip-routing/116264-technote-ios-00.html

Q3. 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

Q4. Which three statements about IS-IS are true? (Choose three.)

A. IS-IS is not encapsulated in IP.

B. IS-IS is directly encapsulated in the data link layer.

C. 0XFEFE is used in the Layer 2 header to identify the Layer 3 protocol.

D. IS-IS uses protocol ID 93.

E. IS-IS can be used to route the IPX protocol.

F. IS-IS is an IETF standard.

Answer: A,B,C

Explanation:

IS-IS is an Interior Gateway Protocol (IGP) for routing OSI. IS-IS packets are not encapsulated in CLNS or IP but are encapsulated directly in the data-link layer. The IS-IS protocol family is OSI, and values such as 0xFE and 0xFEFE are used by the data-link protocol to identify the Layer 3 protocol as OSI.

Reference: http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.sh tml

Q5. Refer to the exhibit.

R1 is performing mutual redistribution, but OSPF routes from R3 are unable to reach R2. Which three options are possible reasons for this behavior? (Choose three.)

A. R1 requires a seed metric to redistribute RIP.

B. The RIP version supports only classful subnet masks.

C. R1 is filtering OSPF routes when redistributing into RIP.

D. R3 and R1 have the same router ID.

E. R1 and R3 have an MTU mismatch.

F. R2 is configured to offset OSPF routes with a metric of 16.

Answer: A,C,F

Explanation:

A. RIP requires a seed metric to be specified when redistributing routes into that protocol. A seed metric is a "starter metric" that gives the RIP process a metric it can work with. The OSPF metric of cost is incomprehensible to RIP, since RIP's sole metric is hop count. We've got to give RIP a metric it understands when redistributing routes into that protocol, so let's go back to R1 and do so.

C. Filtering routes is another explanation, if the routes to R2 are boing filtered from being advertised to R1.

F. If the metric is offset to 16, then the routes will have reached the maximum hop count when redistributed to RIP. The max hop count for RIP is 16.

Q6. Which two loop-prevention mechanisms are implemented in BGP? (Choose two.)

A. A route with its own AS in the AS_PATH is dropped automatically if the route reenters its own AS.

B. A route with its own cluster ID in the CLUSTER_LIST is dropped automatically when the route reenters its own AS.

C. The command bgp allowas-in enables a route with its own AS_PATH to be dropped when it reenters its own AS.

D. The command bgp bestpath as-path ignore enables the strict checking of AS_PATH so that they drop routes with their own AS in the AS_PATH.

E. The command bgp bestpath med missing-as-worst assigns the smallest possible MED, which directly prevents a loop.

Answer: A,B

Explanation:

When dealing with the possibility of routing updates making their way back into an AS, BGP relies on the information in the AS_path for loop detection. An update that tries to make its way back into the AS it was originated from will be dropped by the border router. With the introduction of route reflectors, there is a potential for having routing loops within an AS. A routing update that leaves a cluster might find its way back inside the cluster. Loops inside the AS cannot be detected by the traditional AS_path approach because the routing updates have not left the AS yet. BGP offers two extra measures for loop avoidance inside an AS when route reflectors are configured.

Using an Originator ID

The originator ID is a 4-byte, optional, nontransitive BGP attribute (type code 9) that is created by the route reflector. This attribute carries the router ID of the originator of the route in the local AS. If, because of poor configuration, the update comes back to the originator, the originator ignores it.

Using a Cluster List

The cluster list is an optional, nontransitive BGP attribute (type code 10). Each cluster is represented with a cluster ID.

A cluster list is a sequence of cluster IDs that an update has traversed. When a route reflector sends a route from its clients to nonclients outside the cluster, it appends the local cluster ID to the cluster list. If the route reflector receives an update whose cluster list contains the local cluster ID, the update is ignored. This is basically the same concept as the AS_path list applied between the clusters inside the AS.

Reference: http://borg.uu3.net/cisco/inter_arch/page11.html

Q7. Which option is the default point of insertion for the BGP cost community?

A. before best path calculation

B. after best path calculation

C. after the IGP metric comparison

D. after the router ID comparison

Answer: C

Q8. Which three statements about bridge assurance are true? (Choose three.)

A. Bridge assurance must be enabled on both ends of a link.

B. Bridge assurance can be enabled on one end of a link or on both ends.

C. Bridge assurance is enabled on STP point-to-point links only.

D. Bridge assurance is enabled on STP multipoint links only.

E. If a bridge assurance port fails to receive a BPDU after a timeout, the port is put into a blocking state.

F. If a bridge assurance port fails to receive a BPDU after a timeout, the port is put into an error disabled state.

Answer: A,C,E

Explanation:

Bridge Assurance is enabled by default and can only be disabled globally. Also, Bridge Assurance can be enabled only on spanning tree network ports that are point-to-point links.

Finally, both ends of the link must have Bridge Assurance enabled.

With Bridge Assurance enabled, BPDUs are sent out on all operational network ports, including alternate and backup ports, for each hello time period. If the port does not receive a BPDU for a specified period, the port moves into the blocking state and is not used in the root port calculation. Once that port receives a BPDU, it resumes the normal spanning tree transitions.

Reference:

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guid e/cli/CLIConfigurationGuide/SpanningEnhanced.html

Q9. What is the most common use for route tagging in EIGRP?

A. to determine the route source for management purposes

B. to change the metric of a prefix

C. to filter routes in order to prevent routing loops

D. to modify path selection for certain classes of traffic

Answer: C

Q10. When you enable the MPLS Multi-VRF feature, which two supported routing protocols can be used to exchange routing information between PE routers and CE routers? (Choose two.)

A. BGP

B. RIP

C. OSPF

D. EIGRP

E. IS-IS

Answer: A,B