Rebirth 642-885 Preparation Labs 2021

NEW QUESTION 1
When enabling interdomain multicast routing, which two statements are correct? (Choose two.)

• A. Multiprotocol BGP is used instead of PIM SM to build the intradomain and interdomain multicast distribution trees
• B. Use MSDP to enable the RPs from different domains to exchange information about active multicast sources
• C. MSDP SA packets are sent between the multiprotocol BGP peers
• D. Noncongruent unicast and multicast topologies can be supported using multiprotocol BGP

Answer: BD

Explanation:
http://prakashkalsaria.wordpress.com/2010/08/11/mbgp-msdp/
MSDP In the PIM-SM model, multicast sources and receivers must register with their local RP. Actually, the router closest to the sources or receivers registers with the RP, but the key point to note is that the RP knows about all the sources and receivers for any particular
group. RPs in other domains have no way of knowing about sources located in other domains. MSDP is an elegant way to solve this problem.
MSDP is a mechanism that allows RPs to share information about active sources. RPs know about the receivers in their local domain. When RPs in remote domains hear about the active sources, they can pass on that information to their local receivers and multicast data can then be forwarded between the domains. A useful feature of MSDP is that it allows each domain to maintain an independent RP that does not rely on other domains, but it does enable RPs to forward traffic between domains. PIM-SM is used to forward the traffic between the multicast domains.
The RP in each domain establishes an MSDP peering session using a TCP connection with the RPs in other domains or with border routers leading to the other domains. When the RP learns about a new multicast source within its own domain (through the normal PIM register mechanism), the RP encapsulates the first data packet in a Source-Active (SA) message and sends the SA to all MSDP peers. The SA is forwarded by each receiving peer using a modified RPF check, until the SA reaches every MSDP router in the interconnected networks—theoretically the entire multicast internet. If the receiving MSDP peer is an RP, and the RP has a (*, G) entry for the group in the SA (there is an interested receiver), the RP creates (S, G) state for the source and joins to the shortest path tree for the source. The encapsulated data is decapsulated and forwarded down the shared tree of that RP. When the packet is received by the last hop router of the receiver, the last hop router also may join the shortest path tree to the source. The MSDP speaker periodically sends SAs that include all sources within the own domain of the RP
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.2/routing/configuration/guide/rc32bgp.html
Multiprotocol BGP
Multiprotocol BGP is an enhanced BGP that carries routing information for multiple network layer protocols and IP multicast routes. BGP carries two sets of routes, one set for unicast routing and one set for multicast routing.
The routes associated with multicast routing are used by the Protocol Independent Multicast (PIM) feature to build data distribution trees.
Multiprotocol BGP is useful when you want a link dedicated to multicast traffic, perhaps to limit which resources are used for which traffic. Multiprotocol BGP allows you to have a unicast routing topology different from a multicast routing topology providing more control over your network and resources.
In BGP, the only way to perform interdomain multicast routing was to use the BGP infrastructure that was in place for unicast routing. Perhaps you want all multicast traffic exchanged at one network access point (NAP).
If those routers were not multicast capable, or there were differing policies for which you wanted multicast traffic to flow, multicast routing could not be supported without multiprotocol BGP.
Note It is possible to configure BGP peers that exchange both unicast and multicast network layer reachability information (NLRI), but you cannot connect multiprotocol BGP clouds with a BGP cloud. That is, you cannot redistribute multiprotocol BGP routes into BGP.

NEW QUESTION 2
Which additional feature is provided using MLDv2 that is not available in MLDv1?

• A. Multicast Address Specific Queries
• B. Source filtering
• C. Done messages
• D. Report messages

Answer: B

Explanation:
• PIM-SSM is made possible by IGMPv3 and MLDv2. Hosts can now indicate interest in specific sources using IGMPv3 and MLDv2. SSM does not require a rendezvous point (RP) to operate.

NEW QUESTION 3
The IPv6 2002::/16 prefix is used in which kind of implementations?

• A. 6 RD
• B. 6 to 4
• C. NAT 64
• D. IPv6 Multicast

Answer: B

NEW QUESTION 4
A network engineer for an ISP wants to reduce the number of iBGP adjacencies. A merge is taking place with another ISP network, so the network engineer needs to make both ASNs look like a single network for the Internet. Which BGP technology is most suitable?

• A. route reflector
• B. confederation
• C. clustering
• D. peer group

Answer: B

NEW QUESTION 5
A network engineer must deploy an iBGP-based cloud region configuration by means of templates to reduce the overall BGP CLI required. Which three commands represent a basic configuration for a BGP peer session template on a regular Cisco IOS instance? (Choose three.)

• A. template peer-session session-template-name
• B. remote-as as-number
• C. neighbor-family config template
• D. peer-family config template
• E. as-override
• F. timers keepalive-interval hold-time

Answer: ABF

NEW QUESTION 6
Which protocol can be used to secure multicast in a group multicast solution where group key management is needed for secure key exchange?

• A. DOI
• B. ISAKMP
• C. GDOI
• D. IPsec

Answer: C

NEW QUESTION 7
Refer to the Cisco IOS-XR configuration exhibit.

The Cisco IOS-XR router is unable to establish any PIM neighbor relationships. What is wrong with the configuration?

• A. The configuration is missing:interface gi0/0/0/0 ip pim sparse-mode interface gi0/0/0/1 ip pim sparse-mode interface loopback0 ip pim sparse-mode
• B. The configuration is missing: multicast-routingaddress-family ipv4 interface gi0/0/0/0 enableinterface gi0/0/0/1 enable
• C. The auto-rp scoping configurations should be set to 1 not 16
• D. The RP address has not been configured using the rp-address router PIM configuration command
• E. PIM defaults to dense mode operations only, so PIM sparse mode must be enabled using the pim sparse-mode router PIM configuration command

Answer: B

NEW QUESTION 8
Which multicast routing protocol supports dense mode, sparse mode and bidirectional mode?

• A. DVMRP
• B. MOSPF
• C. PIM
• D. MP-BGP
• E. MSDP

Answer: C

NEW QUESTION 9
Refer to the exhibit.

The following multicast IP addresses map to which multicast MAC address?

• A. 01:00:5E:8A:00:01
• B. 01:00:5E:0A:00:01
• C. 01:00:5E:7A:00:01
• D. 01:00:5E:05:00:01

Answer: B

NEW QUESTION 10
Which field in the IPv6 header can be used to set the DSCP value?

• A. Flow Label
• B. Type of Service
• C. Traffic Class
• D. Precedence
• E. EXP

Answer: C

Explanation:
Traffic Class
The Traffic Class field is an 8 bit field that is used to signify the importance of the data contained within this specific packet. With IPv4, this information was signified with the TOS field and supported both IP precedence and Differentiated Services Code Point (DSCP). The Traffic Class field used with IPv6 supports DSCP solely; this specification uses the first 6 bits to indicate the Per Hop Behavior (PHB) of the contained data; these PHB’s are defined in RFC 2474 and its additions.

NEW QUESTION 11
When configuring BFD, the multiplier configuration option is used to determine which value?

• A. The retry interval
• B. The number of BFD packets that can be lost before the BFD peer is declared "down"
• C. The minimum interval between packets accepted from the BFD peers
• D. The number of BFD echo packets that will be originated by the router
• E. The number of routing protocols that will use BFD for fast peer failure detection

Answer: B

NEW QUESTION 12
Refer to the configuration exhibit, taken from a Cisco IOS-XR router.

Which configuration change is required to properly enable this router as the signaling router for implementing source-based RTBH filtering?

• A. Set community (no-export) in the route policy
• B. Pass in the route policy
• C. Set local-preference 1000 in the route policy
• D. The 192.0.2.1/32 static route should be tagged as 666 (tag 666)

Answer: A

NEW QUESTION 13
Which types of multicast distribution tree can PIM-SM use?

• A. Only shared tree rooted at the source
• B. Only shared tree rooted at the RP
• C. Only shortest path tree rooted at the RP
• D. Shared tree rooted at the source and shortest path tree switchover
• E. Shared tree rooted at the RP and shortest path tree switchover
• F. Shared tree rooted at the first-hop router and shortest path tree rooted at the RP

Answer: E

NEW QUESTION 14
An engineer is enabling multicast routing across an entire core infrastructure. Which two
commands enable multicast routing on Cisco IOS XE instances? (Choose two.)

• A. ip multicast-routing
• B. ip multicast-routing vrf global
• C. interface type slot/path_id ip pim sparse-mode
• D. interface type slot/path_id ip cgmp
• E. interface type slot/path_id ip pim dense-mode
• F. ip mroute-cache

Answer: AC

NEW QUESTION 15
A junior network engineer has just configured a new IBGP peering between two Cisco ASR9K PE routers in the network using the loopback interface of the router, but the IBGP neighborship is not able to be established. Which two verification steps will be helpful in troubleshooting this problem? (Choose two.)

• A. Verify that the network command under router BGP is configured correct on each router for announcing the router's loopback interface in BGP
• B. Verify that the ibgp-multihop command under the BGP neighbor is configured correctly on each router
• C. Verify that the loopback interfaces are reachable over the IGP
• D. Verify that the update-source loopback command under the BGP neighbor is configured correctly on each router
• E. Verify that the ttl-security command under the BGP neighbor is configured correctly on each router to enable the router to send the BGP packets using a proper TTL value
• F. Verify that the UDP port 179 traffic is not being blocked by an ACL or firewall between the two IBGP peers

Answer: CD

NEW QUESTION 16
Each router (RTA, RTB, and RTC) has one iBGP adjacency with the route reflector router RTD. Router RTC has an iBGP route advertised by RTA, but the same route is missing from RTB. Thenetwork engineer verifies that route filtering does not deny the route advertisement. Which action corrects the problem?

• A. RTD(config-router)#neighbor 192.168.1.1 route-reflector-client RTD(config-router)#neighbor 192.168.1.1 description RTA RTD(config-router)#neighbor 192.168.1.2 route-reflector-client RTD(config-router)#neighbor 192.168.1.2 description RTB
• B. RTC(config-router)#neighbor 192.168.1.4 route-reflector-client RTC(config-router)#neighbor 192.168.1.4 description RTD
• C. RTA(config-router)#neighbor 192.168.1.4 route-reflector-client RTA(config-router)#neighbor 192.168.1.4 description RTDRTB(config-router)#neighbor 192.168.1.4 route-reflector-client RTB(config-router)#neighbor 192.168.1.4 description RTD
• D. RTB(config-router)#neighbor 192.168.1.3 route-reflector-client RTB(config-router)#neighbor 192.168.1.3 description RTC
• E. RTB(config-router)#neighbor 192.168.1.3 route-reflector-client RTB(config-router)#bgp cluster-id 192.168.1.2RTB(config-router)#no bgp client-to-client reflection

Answer: A

NEW QUESTION 17
Which of the following can be used by dual-stack service providers supporting IPv4/IPv6
customers with dual-stack hosts using public IPv6 addresses and private IPv4 addresses?

• A. NAT64
• B. 6RD
• C. 6to4 tunnels
• D. Carrier-grade NAT

Answer: D

Explanation:
Carrier Grade NAT is a large-scale NAT, capable of providing private-IPv4-to-public-IPv4 translation in the order of millions of translations. Carrier Grade NAT can support several hundred thousand subscribers with the bandwidth throughput of at least 10Gb/s full-duplex. With IPv4 addresses reaching depletion, Carrier Grade NAT is vital in providing private IPv4 connectivity to the public IPv4 internet. In addition, Carrier Grade NAT is not limited to IPv4 NAT; it can also translate between IPv4 and IPv6 addresses.

NEW QUESTION 18
Refer to the exhibit.

Which configuration ensures that RR2 does not send the same updates to PE2 that RR1 learns via PE1?

• A. RR1 and RR2 should have different router IDs.
• B. RR1 and RR2 should have different originator IDs.
• C. RR1 and RR2 should have the same router IDs.
• D. RR1 and RR2 should have the same cluster IDs.

Answer: D

NEW QUESTION 19
Refer to the exhibit.




Which two statements are correct regarding the multicast operations on the router that is the RP? (Choose two.)

• A. It is using IGMPv3
• B. The IGMP query interval is set to 125 seconds
• C. It is using the IPv4 unicast routing table to perform the RPF checks
• D. Static multicast routes are configured on the RP

Answer: AC

Explanation:
#show ip mroute
#show ip pim interface
#show ip igmp group
#show ip pim neighbor

NEW QUESTION 20
What must occur before an (S,G) entry can be populated in the multicast routing table?

• A. The (*,G) entry must have timed out
• B. The (*,G) entry OIL must be null
• C. The router must be directly connected to the multicast source
• D. The parent (*,G) entry must be created first

Answer: D

NEW QUESTION 21
Which two actions result when a network administrator attempts to ping an IPv6 host on the LAN? (Choose two.)

• A. ARP is used to determine the MAC address of the destination host.
• B. Neighbor Discovery is used to determine the MAC address of the destination host.
• C. Neighbor Solicitation messages are sent out by the source host to determine the data link-layer address of the destination host.
• D. Neighbor Advertisement messages are sent by the source host to announce its presence on the local link.
• E. Router Solicitation messages are sent out on a specific multicast address to request the data link-layer address of the target device.
• F. Router Solicitation messages are sent to the local router on the network segment to request data link-layer information about the destination host.

Answer: BC

NEW QUESTION 22
The bsr-border router PIM interface configuration command is used for what purpose?

• A. To enable the router as the candidate RP
• B. To enable the router as the candidate BSR
• C. To enable the router as the BSR mapping agent
• D. To set up an administrative boundary to prevent BSR messages from being sent out through an interface
• E. To define a boundary to restrict the RP discovery and announcement messages from being sent outside the PIM-SM domain

Answer: D

NEW QUESTION 23
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